Create a bootable pendrive with the latest Debian11 netinst image on it
Ensure the Nimbustor's LAN port is connected to your network - as it will need internet access during setup to fetch packages
Power down the Nimbustor
Plug a monitor into the HDMI port
Plug in the USB installer pendrive and the USB hdd/ssd you'll be installing to
Plug a USB keyboard into the 3rd USB port
Power up the unit, and keep hitting ESC on your keyboard until you get the BIOS setup screen ( you won't see any prompts as ex-factory the unit is set for silent boot)
in the BIOS settings make the following changes :
Boot
quick boot -> change to disabled
quiet boot -> change to disabled
network stack -> leave on disabled
power up in standby support -> leave on disabled
add boot options -> leave on auto
acpi selection -> leave on acpi5.0
usb boot - leave on enabled
uefi fast boot -> change to disabled
timeout -> leave on 0
automatic failover -> leave on enabled
boot order -> move usb cdrom and usb hdd to top, sdcard to bottom
sdcard/emmc -> untick
internal sata port 0 -> ticked
uefi shell -> unticked
usb hdd -> ticked
advanced / thermal
automatic thermal reporting -> leave on disabled
change critical trip point to 95 ( was 110 )
change passive trip point to 85 ( was 65 )
change active trip point to 85 ( was 95 )
DPTF -> leave on disabled ( linux doesn't really support DPTF )
advanced / cpu config
DTS -> change to enabled
leave everything else as is
advanced /security config
SGX -> change to disabled ( was 'software defined' )
advanced / system component
embedded power instrumentation -> change to enabled
leave everything else as is
advanced / south cluster / miscellaneous configuration
hide un-used LPSS devicse -> leave on enabled
PSS device - IMPJ003 setting -> change to enabled
exit and save changes ( this will cause the unit to reboot ) and proceed to the next step
My fear was unwarranted. I got the BIOS setup screen my slowly tapping F2. It first looked like that was only supported on the front USB port, but it seems I somehow didn't tap in the right rhythm when the keyboard was attached to one of the backside USB ports.
Testing again, it is enough to wait until the TianoCore logo disappears and then tap F2.
Here are the locations for some of the options you advise to change:
Main -> Boot Features:
quick boot -> change to disabled
quiet boot has probably been replaced with Diagnostic Splash Screen and Diagnostic Summary Screen. I switched it on for entertainment ;-)
Main -> Network Stack:
network stack -> leave on disabled
Boot
boot order -> move usb cdrom and usb hdd to top, sdcard to bottom
emmc card -> untick with shift + 1
I did't find your other settings, but since I had to switch between two machines, I may have overlooked some. Definitively the BIOS is changed a lot.