No boot without monitor

Hi, I made a fresh install of OMV 7.0-20 (Sandworm) with not any problem on a desktop. I want to use this desktop without monitor but when I disconnect the monitor, it will not boot. I know this is common in Linux and I had this before with Ubuntu on this same desktop. Uncomment the line GRUB_TERMINAL=console in the grub file (and update grub) was enough to solve the problem. But now on this install it doesn't work. I've tried some variations including the solution in this thread Fehler beim Booten ohne Monitor however without any result. When I uncomment the beep in the grub file, it will give a beep as soon the grub starts. Without the monitor it won't even beeb, I guess grub is not started at all. I looked in the BIOS but I'm not familiar with that, didn't found something either.

Does anyone has a clue? All the various suggestion I found on the web seems to work in their cases but not here. I made several fresh installs again to start over again. I also made a fresh Ubuntu install on the same desktop and after adjusting the grub file booting without monitor worked fine. I spent already hours on this and is frustrating me..... a bit

Thanks for the response. It is odd but I give up. I tried on an other old desktop I have around and with this desktop I had no problem to boot after adjusting the grub file. I also switched back to the latest stable version but that made no difference. Somehow it is something in the desktop that with Ubuntu it does work but not with OMV. I will give it a try with a dummy.