csrutil disable
Restart computer
In the terminal, type
sudo open /Applications/TextEdit.app /System/Library/LaunchDaemons/com.apple.ManagedClient.enroll.plist
change
<key>com.apple.ManagedClient.enroll</key>
<true/>
to
<key>com.apple.ManagedClient.enroll</key>
<false/>
So that the changes take effect
I wanted to follow up on my original post here with my eventual solution.
I called the IT number in the Remote Management popup (twice) and never heard back from them.
I decided to try my 'air gapped' idea and I downloaded the installer for Ventura (and Sonoma) and set up the USB installers for each, then I disconnected the Ethernet cable from the computer and turned off my router to remove any "known" Wi-Fi networks.
After the offline clean install I was able to get all the way through the setup dialogs with no Remote Management intervention.
I looked at the system settings mentioned elsewhere on this thread and noted that after my clean install of the OS Remote Management defaulted to "off' and that no profiles were present.
I migrated all my data back onto the drive and re-connected to the internet. No popups, no Remote Management issues at all. I even updated the OS after all this and had no more interference.
The lesson here for me was that I learned a lot about Remote Management, a lot that I really didn't want to know..!
Had I known Remote Management existed before I tried to update the OS, and that defeating it was as possibly as easy as turning off a system preference, my life would have been so much better over these last 3 days.
I'm grateful for all the replies here, though I'm still not clear on how certain aspects of Remote Management work...
Questions:
Am I free and clear now?
In order for Remote management require a profile to be set up on the individual machine (by IT for example) or is there some sort of serial number database that was used to identify my second-hand computer as belonging to Pinterest (in my case), with the possibility that this might happen again?
Thanks again.