Force RGB Color on M1 Mac

Force-RGB-Color-on-M1-Mac.md

Force RGB Color on M1 Mac

How to Force RGB Color Output instead of YPbPr on your M1 Apple Silicon Mac for an External Monitor.

This step-by-step video tutorial will guide you through the procedure of forcing RGB color output on your M1 Mac.

Here is the direct link to the video tutorial: https://www.youtube.com/watch?v=Z1EqH3fd0V4

The video also has Closed Captions (Subtitles) that you can enable, to make it easier to follow if needed.

Please note that you're doing any changes on your own risk.

Terminal commands used in the video

Here are each of the Terminal commands mentioned in the tutorial, so that you can just copy and paste them:

open /Library/Preferences

plutil -convert xml1

plutil -convert binary1

plutil -lint

The step-by-step procedure on how to force RGB Color Output on M1 and M2 based Macs with Terminal commands

1. Open Terminal and use this command to make Finder select the displays plist file:
   open -R /Library/Preferences/com.apple.windowserver.displays.plist

2. Drag and drop the com.apple.windowserver.displays.plist file to Desktop manually. Don't use the cp command, as it won't add your current user with writing privileges.

3. Convert the file to XML:
   plutil -convert xml1 ~/Desktop/com.apple.windowserver.displays.plist

4. Open the converted file with the default plain text editor (avoid using the built-in TextEdit app if possible, since it might modify the file and make it unreadable by the system)
   open -t ~/Desktop/com.apple.windowserver.displays.plist
   or
   open -a CotEditor.app ~/Desktop/com.apple.windowserver.displays.plist

5. Copy and paste the missing LinkDesription Key under the current display (check the screenshot below for an example of how it should look like):
   

				<key>LinkDescription</key>
				<dict>
					<key>BitDepth</key>
					<integer>8</integer>
					<key>EOTF</key>
					<integer>0</integer>
					<key>PixelEncoding</key>
					<integer>0</integer>
					<key>Range</key>
					<integer>1</integer>
				</dict>

6. Save the file and then convert it to binary again:
   plutil -convert binary1 ~/Desktop/com.apple.windowserver.displays.plist

7. Check if the plist file is valid:
   plutil -lint ~/Desktop/com.apple.windowserver.displays.plist

8. Open the /Library/Preferences/ folder again:
   open /Library/Preferences/

9. Drag and drop the updated com.apple.windowserver.displays.plist file from Desktop to the Library folder manually. Don't use the cp command, as it won't add your current user with writing privileges.

10. Right Click on the com.apple.windowserver.displays.plist file in the Library folder and click on Get Info

11. Check the boxes for Stationery and Locked.

12. Reboot the Mac.

That's it!

(Alternative) Terminal commands to force RGB Color Output on M1 and M2 based Macs and workaround for losing RGB color after waking up from sleep

1. Open Terminal

2. Paste the following commands to edit the User's displays plist file com.apple.windowserver.displays.[UUID].plist using the built-in PlistBuddy function in macOS:

/usr/libexec/PlistBuddy -c "add DisplaySets:Configs:DisplayConfig:DisplayConfig:DisplayConfig:LinkDescription:BitDepth integer" ~/Library/Preferences/ByHost/com.apple.windowserver.displays.*.plist
/usr/libexec/PlistBuddy -c "set DisplaySets:Configs:DisplayConfig:DisplayConfig:DisplayConfig:LinkDescription:BitDepth 8" ~/Library/Preferences/ByHost/com.apple.windowserver.displays.*.plist
/usr/libexec/PlistBuddy -c "add DisplaySets:Configs:DisplayConfig:DisplayConfig:DisplayConfig:LinkDescription:EOTF integer" ~/Library/Preferences/ByHost/com.apple.windowserver.displays.*.plist
/usr/libexec/PlistBuddy -c "add DisplaySets:Configs:DisplayConfig:DisplayConfig:DisplayConfig:LinkDescription:PixelEncoding integer" ~/Library/Preferences/ByHost/com.apple.windowserver.displays.*.plist
/usr/libexec/PlistBuddy -c "add DisplaySets:Configs:DisplayConfig:DisplayConfig:DisplayConfig:LinkDescription:Range integer" ~/Library/Preferences/ByHost/com.apple.windowserver.displays.*.plist

3. Reboot your Mac
   
   

(Workaround) If your Mac loses RGB color after waking up from sleep mode, either Reboot your Mac (recommended) or use this Terminal command to stop the WindowServer and login again (not recommended):

sudo killall -HUP WindowServer

End result

The end result is having your M1 mac output RGB color to your external monitor instead of YPbPr, potentially making the colors more accurate and the text a bit more crisp, even on older 1080p monitors.

Hopefully this tutorial would be useful to someone.

Please feel free to ask in the comment section if you have any questions regarding this procedure.

Background

While doing a lot of testing on how the Dual-Cable workaround makes RGB to work on M1, I've discovered what changes it makes to macOS, and managed to create a more streamlined workaround without the need to use a second cable.

To make things easier, I've created a step-by-step video tutorial of the whole procedure that should force RGB color output on your M1 Mac connected to an external monitor, and works on an HDMI-to-HDMI cable connection.

Credits

Big thanks goes to the amazing community and all their help over the years to solve issues like this:
https://gist.github.com/ejdyksen/8302862
https://gist.github.com/adaugherity/7435890

Useful Sources

Apple Open Source Project Files for Displays and Graphics
https://opensource.apple.com/source/IOKitUser/IOKitUser-1445.60.1/graphics.subproj/IODisplayLib.c
https://opensource.apple.com/source/IOGraphics/IOGraphics-517.17/IOGraphicsFamily/IOFramebuffer.cpp.auto.html

How to Edit and Convert binary plist files
http://hints.macworld.com/article.php?story=20050803111126899
https://apple.stackexchange.com/questions/155393/how-to-beautify-binary-dict-files
https://discussions.apple.com/thread/1768480

How to Edit plist files using defaults and PlistBuddy
https://ss64.com/osx/defaults.html
https://github.com/mathiasbynens/dotfiles/blob/master/.macos

Apps based on this method

@sudowork has created an awesome script written in Phyton that automates the steps and checks for duplicate files.
You can find more info about it here: https://github.com/sudowork/fix_m1_rgb

@dangh has created an alernative script for fishshell.
You can find more info about it here: https://github.com/dangh/force-rgb.fish

@GetVladimir I've also created a Shortcut to Force RGB Color Output using the built-in Shortcuts app.
You can find how to create the Shortcut here: https://gist.github.com/GetVladimir/c89a26df1806001543bef4c8d90cc2f8?permalink_comment_id=4531552#gistcomment-4531552

@entropyconquers has created a script based on this method written in Phyton that automates the steps, makes a backup and checks for duplicate files.
You can find more info about it here: https://github.com/entropyconquers/Force-RGB-Color-on-M1-M2-Mac-Script

Additional notes

Multiple PixelEncoding and Range keys in the same plist file
Note that there might be multiple instances of the PixelEncoding and Range keys in the same file, one for each output of your monitor and for different AirPlay devices. You might need to update the integer on each one to get RGB color output on all displays.

Getting RGB color only before login
There might be multiple duplicate plist files with the same name in different locations.

Make sure that you only have the main modified file in:
/Library/Preferences

Then make a backup and remove duplicate displays plist files from these locations (if any):
~/Library/Preferences
or
/Users/username/Library/Preferences
and
/Users/username/Library/Preferences/ByHost

Please note that you'll need to have administrator privileges in order to modify the file in /Library/Preferences. Thanks goes to @keegandent and @StrategicalIT for pointing this out.

Updates regarding macOS Monterey

USB-C to DisplayPort
From what I've seen, it seems that macOS Monterey 12.0.1 finally outputs RGB color by default on some monitors when using USB-C to DisplayPort cable on M1 Apple Silicone Macs.

You might need to make a backup and delete these 2 files:
/Library/Preferences/com.apple.windowserver.displays.plist
and
/Users/yourname/Library/Preferences/ByHost/com.apple.windowserver.displays.[UDID].plist

Restart your Mac and it should properly output RGB color on the monitor on the next boot.

HDMI to HDMI
The situation with HDMI seems to got a bit more complicated. Now the whole section for the LinkDescription might be missing from the com.apple.windowserver.displays.plist on a clean install and doesn't seem to be recreated when rotating the screen either.

Luckily, the solution still works, but you might need to manually add this whole section in the displays plist file:

					<key>LinkDescription</key>
					<dict>
						<key>BitDepth</key>
						<integer>8</integer>
						<key>EOTF</key>
						<integer>0</integer>
						<key>PixelEncoding</key>
						<integer>0</integer>
						<key>Range</key>
						<integer>1</integer>
					</dict>

The section usually goes right under the CurrentInfo key, and it should look something like this:

This should get your RGB color output working on M1 Mac mini, even when connected with HDMI to HDMI cable.

Multiple monitors when one them is using HDMI to HDMI
Additional thanks goes to @somogyi-ede who tested this with multiple monitors and confirmed that the LinkDescription key needs to be added under each monitor instance in order for all of them to receive RGB color output. Link to the comment

Updates regarding macOS 13 Ventura

USB-C to DisplayPort
The macOS 13 Ventura beta seems to outputs RGB color by default on some monitors when using USB-C to DisplayPort cable on M1 Apple Silicone Macs.

You might need to make a backup and delete these 2 files:
/Library/Preferences/com.apple.windowserver.displays.plist
and
/Users/yourname/Library/Preferences/ByHost/com.apple.windowserver.displays.[UDID].plist

Restart your Mac and it should properly output RGB color on the monitor on the next boot.

HDMI to HDMI
Similar as macOS Monterey, the situation with HDMI on macOS Venturs seems a bit more complicated. Usually the whole section for the LinkDescription might be missing from the com.apple.windowserver.displays.plist on a clean install and doesn't seem to be recreated when rotating the screen either.

Luckily, the solution still works, and you still need to manually add this whole section in the displays plist file:

					<key>LinkDescription</key>
					<dict>
						<key>BitDepth</key>
						<integer>8</integer>
						<key>EOTF</key>
						<integer>0</integer>
						<key>PixelEncoding</key>
						<integer>0</integer>
						<key>Range</key>
						<integer>1</integer>
					</dict>

The section usually goes right under the CurrentInfo key, and it should look something like this:

This should get your RGB color output working on M1 Mac mini, even when connected with HDMI to HDMI cable.

(Optional) Lock the plist file and set it as stationary
After the macOS Ventura 13.3 update, the plist file seems to get overwritten on reboot.

After you make the edits in the file, you can try setting the file /Library/Preferences/com.apple.windowserver.displays.plist as Stationery pad and Locked, so that it doesn't get overwritten on every reboot

To do this, right click on the plist file, click on Get Info and check the boxes next to Stationery pad and Locked

This requires further testing and might cause some issues, like not being able to remember new resolutions or display settings. Please note that you're making any changes at your own risk.

Updates regarding macOS 14 Sonoma Beta

USB-C to DisplayPort
The macOS 14 Sonoma seems to outputs RGB color by default when using USB-C to DisplayPort cable.

HDMI to HDMI
The macOS 14 Sonoma seems to outputs YCbCr color by default when using HDMI to HDMI cable.

• Forcing RGB Color Output still seems to work with the original procedure of modifying the plist files

• Modifying the display plist files still works with the alternative version

• After the plist files are modified, putting the Mac to sleep and waking it, it seem to keep the RGB Color output (this seems to be fixed at least on a M1 Mac mini)

If you have any additional questions, please feel free to contact me.

@joevt thank you so much for the suggestion and for the app! This is pretty useful.

@kadepig thanks for the update and the info on Mojave and MiniDP-to-HDMI.

Let us know how it goes with the suggestion from @joevt or with Bootcamp if you decide to test it

@GetVladimir Thanks. I now try to use "windows to go" to install win10 on an external u disk, so that the disk of my mac won't be changed. However it will takes a long time to create windows to go usb drive.

@joevt Thanks for the advise. Would you like to tell me what is "a DisplayPort 1.4 MST hub"? Does the hub contains HDMI or mini DP port in one side when having DP 1.4 male port in the other side? And I have tried the mini DP to DP 1.4 cables which gives the same resolution 4K and 24Hz before.

@GetVladimir I just installed win10, via mini dp to dp cable, win10 supports up to 4K 60Hz, and via hdmi to hdmi, up to 4K 30Hz.

It seems the macOS can't recognize the right information of the monitor via mini dp to dp cable.

@kadepig that is awesome! Thanks for the info and good to know that it supports 4K 60Hz.

macOS always seemed to have issues with detecting monitors properly and setting the correct color output, resolution and refresh rate.

If they can't get it to work, they should just allow all this to be set manually in the System Settings, without arbitrary restrictions

@kadepig I don't think an MST hub will help in your case since the display is accepting 4 lanes of HBR2 which should be sufficient for 4K60.

The AllRez output shows two displays connected to your Intel MacBook Pro 2015.

Monitor[0] is the built-in display (DisplayVendorID, DisplayProductID, DisplayProductName), it has dimensions (dims) 2560x1600, is 60Hz with pixel clock 268.500MHz (DetailedTimingInformation), and connects as HBR (LINK_BW_SET) x4 (LANE_COUNT_SET). The connector doesn't have timing limits (Hz and kHz are unbounded IOFBTimingRange) except pixel clock max is 348MHz. The Intel GPU (Monitor[0] path) doesn't support DSC (IOFBTimingRange).

Monitor[1] is the GIGABYTE M28U. It has:
macOS accepted scaled modes up to 6720x3780.
macOS accepted resolutions up to 3840x2160 (look at the (not scaled) modes)
macOS accepted refresh rates up to 143.853Hz for 1920x1080 (326.62 MHz).
macOS accepted refresh rates up to 119.879Hz for 2560x1440 (486.29 MHz).
macOS accepted refresh rates up to 24Hz for 3840x2160 (297 MHz which is a HDMI 1.4 timing). This is a problem.
None of the modes use DSC since the Intel GPU doesn't support DSC.

The display is connected with HBR2 x4 using 2560x1440@119.875Hz. It supports HBR3 (02201h MAX_LINK_RATE).
It has DSC support with all the color formats and bits per component, 8 slices at 340 Mp/s = 2720MHz possible and 2560 pixels per slice = 20K width. DSC_MAX_BITS_PER_PIXEL is 0. Maybe that means there's bpp limit? macOS usually always uses 12bpp for DSC.
IOFBTimingRange says the connector supports up to 540MHz pixel clock (normal for Intel DisplayPort 1.2 GPUs). A 4 lane HBR2 connection should support up to 720MHz for 8bpc and 576MHz for 10bpc but 540MHz should be sufficient for 4K60 using CVT-RB timing (533MHz).

edid-decode can be used to decode the EDID (IODisplayEDIDOriginal).

One problem I see in the EDID is that the 3840x2160@60Hz mode uses a pixel clock of 567MHz. To achieve 4K60 for this display connected to an Intel DisplayPort 1.2 GPU in macOS, you'll need to use SwitchResX to create a custom timing that macOS and the Intel GPU will accept (use CVT-RB timing). I don't think 567MHz should be a problem for Apple Silicon Macs since those support HBR3.

EDID says the max refresh is 144Hz and the max pixel clock is 1340 MHz. It says the min & max horizontal refresh rate is 246kHz which needs to be ignored. Hopefully macOS is ignoring this. SwitchResX has options to override the ranges.

The EDID has 144MHz modes for 1080p (326.62Mhz), 1440p (594.88MHz), and 4K (324kHz, 1270.08MHz).

It's got VRR from 48 to 144Hz. If you have a GPU that supports VRR on macOS, then you should see a VRR option for any accepted resolution that has an accepted 144Hz refresh rate. macOS won't let you use VRR for a mode that has a max refresh rate that is less than the max VRR refresh rate.

Besides the Detailed Timings (already discussed), Established Timings, and Standard Timings, the display also has these CTA-861 timings:

    VIC   3:   720x480    59.940060 Hz  16:9     31.469 kHz     27.000000 MHz
    VIC   4:  1280x720    60.000000 Hz  16:9     45.000 kHz     74.250000 MHz
    VIC  47:  1280x720   120.000000 Hz  16:9     90.000 kHz    148.500000 MHz
    VIC  16:  1920x1080   60.000000 Hz  16:9     67.500 kHz    148.500000 MHz
    VIC  63:  1920x1080  120.000000 Hz  16:9    135.000 kHz    297.000000 MHz
    VIC  97:  3840x2160   60.000000 Hz  16:9    135.000 kHz    594.000000 MHz
    VIC 118:  3840x2160  120.000000 Hz  16:9    270.000 kHz   1188.000000 MHz
    VIC  93:  3840x2160   24.000000 Hz  16:9     54.000 kHz    297.000000 MHz
    VIC  32:  1920x1080   24.000000 Hz  16:9     27.000 kHz     74.250000 MHz

So you see where the 4K 24Hz option is coming from. It's the only 4K timing with a pixel clock less than the 540MHz accepted by the macOS Intel GPU driver for your MacBook Pro 2015.

@GetVladimir Thanks! I total agree with you that macOS should not set so many restrictions to an external monitor.

@joevt Many Thanks!

AllRez is so powerful that all the information about compatibility between M28u and MacBook is output! Thanks for your careful reading!

I just download the SwitchResX app, and try to create a custom resolution with 38402160 and UI look likes 19201080 @ 60Hz scaled. Would you like to tell me whether the options "Use simplified settings" and "Interlaced" should be selected? Before reboot, I saved from "File"-"save settings", but the status is "Not installed". I don't know why and after reboot, I can't see HiDP 1920*1080 on the "Current Resolutions".

@joevt I find the status of the custom resolutions is always "not installed". After I click "Activate immediately", it said "Display configuration modified.......All unsaved preferences are thus invalid and have been discarded." I have tried SwitchResX 4.12.2 and 4.10.0.

@kadepig Your settings look correct for the custom resolution. Interlaced is for old TVs. CVT-RB is usually correct for LCDs. GTF is for old CRTs. CVT is also mostly for CRTs. Did you register SwithResX? If not then you may be limited in the number of resolutions you can add. You don't need the scaled modes for now. Just include your custom 3840x2160@60Hz timing. Instead of Activate Immediately you can try just disconnecting and reconnecting the display.

@joevt Thanks for the setup guide and advise.

I use the unregistered SwitchResX. After I deleted all the other custom setting except the 3840x2160@60Hz timing, I disconnected and reconnected the display by replug the cable, and it still reminded me "Display configuration modified. ....been discarded". I also disabled SIP or rebooted, but the status was always "Not installed". Is the version of app(above 4.10.0) not compatible with macOS 10.15.7 or Intel64?

I think 4.10.0 should be fine, but you can easily replace it with the latest 4.12.2. Maybe quit SwitchResX. Then go to /Library/Displays/Contents/Resources/Overrides to delete the overrides for the 1c54 / 2800 product. Then try SwitchResX again.

@joevt Thanks so much!

I deleted all setup about M28U before, and recovered everything from SwitchResX, then reinstalled the latest version 4.12.2 with helper tool. Finally the 4K 60Hz works greatly with custom resolution of SwitchResX.

@GetVladimir
Many thanks for You and joevt have spent a lot of time to help me. Words cannot express my gratitude and appreciation to you!

@kadepig that is awesome! Glad to hear that you got 4K 60Hz working.

Thank you for the comment and thanks goes to @joevt for the solution

Update:
I did two things, it's now RGB, not sure which one really makes the sense:

1. Removed the "MonitorControl" (an application can control monitor's brightness and contrast ratio, may using DDC/CI or something like that). After remove the "MonitorControl", it seems like /Library/Preferences/com.apple.windowserver.displays.plist is not overwritten anymore.
2. I found that the effect file for me is the /Users/yourname/Library/Preferences/ByHost/com.apple.windowserver.displays.[UDID].plist, I edited the file and restart, now it's RGB.

I'm on Ventura. I've tried everything recommended here, deleting all possible duplicate plist files. I've also done a search that includes system files and found no other duplicates.

My Dell S3221QS monitor correctly displays in RGB mode at the MacOS login screen, but as soon as I log in it switches back to YPbPr. The /Library/Preferences/com.apple.windowserver.displays.plist file gets overwritten at login time.

EDIT: I got it working! The key was not to delete the ByHosts version of the file, but to modify it in the same way as the Library/Preferences file.

I have exactly the same issue, RGB before login and YCrBr after login, but the "modify it in the same way" method not working for me, The main /Library/Preferences file still gets overwritten.
I also tried remove these files in ~/Library/Preferences and ~/Library/Preferences/ByHost, still not working.

Any ideas?
MacBook Air M1 2020 + macOS Ventura 13.0.1 + Dell SE3223Q (should similar to S3221QS)

@raaay0608 thank you for your comment.

If there is something that changes the resolution or connection after login (like the dock), it might overwrite the plist file.

Focus on the displays plist file located in the ByHosts folder. This is the one that affects the color output after login.

Try again to delete it or to modify it and see if it makes any changes

Provides some information here:

I seek methods to force RGB, to find out if it's the YCbCr mode makes my monitor flickering on dark scenes:

• https://www.reddit.com/r/macbookpro/comments/r3d7yd/macbook_pro_m1_pro_1016_cores_external_monitor/
• https://forums.macrumors.com/threads/macbook-pro-m1-external-screen-flickering.2325279/

The result for me was no, it still flickering under RGB, but the flickering happens on different scenes, also it seems RGB flickering milder than YCbCr, the YCbCr sometimes flicking dramatically.

I also find a interesting thing that the RGB / YCbCr do affects colors. Under RGB, the color profile with my monitor's name ("SE3223Q") shows same color with the "Color LCD" profile, but they are different under YCbCr.

I'm still seeking for solution about the dark scenes flicking. I would appreciate notifying me for any new information here about the flickering problem.

Also, thanks for creating and maintaining this space, it's really helpful.

@raaay0608 thank you for the additional details and update, and I'm glad that you got RGB color output working.

Regarding the flickering, I'm not sure what is the cause of it.

It will be interesting to see if we can install another OS on the M1/M2 based Macs like ChromeOS/Linux/Windows Arm in the future and see if they solve the issues. This will give us more info on whether it's a hardware or macOS issue

Any solution for colors getting reset to ycbcr after waking up from sleep yet? Using usb-c to displayport cable and modified plist files.
Regretting the update to Ventura...

@Viktor-Osika Thank you for the question.

The bug is still there on macOS Ventura 13.0.1, but there is a new 13.1 update that should be released this week.

@GetVladimir no luck with 13.1 unfortunately

@Viktor-Osika thank you for checking with the update and for the confirmation that it's not fixed

@GetVladimir I can also confirm that the solution does not work for 13.1.

@syifan The solution still seems to work on macOS 13.1, at least for M1 Mac mini and HDMI-to-HDMI connections.

The issue is when waking up from sleep on some devices, especially when connected via a dock.

Could you post more details about your connection and on which device?

I have M1 Mac Mini and a Dell U2713H, directly connecting using an HDMI-to-HDMI connection.

I can briefly get RGB mode to work. But whenever I change anything small in the display setting, the windoeserver plist file entry is updated back to the state without LinkDescription.

Waiting for a solution to this problem.

@syifan thanks for the update and the details! I'm glad to hear that you got RGB color output working on the M1 Mac mini.

That is correct. If you change the resolution from the Settings, it overwrites the plist file.

A workaround for this is to create a backup of the working display plist file, so that you can restore it easily if needed

@GetVladimir What is even more annoying is that the color mode will change back if I turn off the display and turn it back on. Only restarting will fix it.

@syifan Yes, that is indeed a bug since macOS Ventura. It hasn't been fixed with 13.1 either.

What would be best is if the monitor support works out of the box in macOS, so that we don't need to jump through hoops and modify plist files just to make RGB color output working

Hi,
I am using a MacBook Pro M1 with an (old) 27" Monitor (Acer K272HUL), macOS Ventura 13.0.1.
I have tried to add the above section (LinkDescription …) to my com.apple.windowserver.displays.plist to force the output to RGB.
But: After restart the lines just disappear and the output i still flat.
Is there a solution?

@op0815 thank you for your question and the details.

Yes, there are a few things you can try:

• Please make sure to use a plain text editor to make the changes. If you don't have have one, you can use the free, open source CotEditor, that's available on the Mac App Store: https://apps.apple.com/us/app/coteditor/id1024640650?mt=12
• Try to edit both the plist file in:
  /Library/Preferences/com.apple.windowserver.displays.plist
  and in
  /Users/yourname/Library/Preferences/ByHost/com.apple.windowserver.displays.[UDID].plist
• Use a direct USB-C to DisplayPort or USB-C to HDMI cable from the MacBook to the monitor. Avoid using a dock, hub or adapters
• Update to macOS 13.1, just to be on the latest version

Let us know how it goes or if you have any additional questions.

Wish you a Merry Christmas and Happy New Year holidays!

@GetVladimir thank for your tips.

But: Did not work …

• I am using BBedit
• I have edited both files, after the restart (after the update) only the file in the ByHost-folder contained the "LinkDescription"-section, the one in the /Library/Preferences/ this section "disappeared" again
• the monitor is connected by a HDMI cable, I have tried USB-C to HDMI (unfortunately: with Adapter): the monitor "says": No Signal
• I have updated to macOS 13.1

Merry Christmas and Happy New Year to you too!