I got it working!
I've cloned the physical disk to an image using the guide from the wiki - Physical to VM conversion.
It is a Linuxmint 20.1 and it worked using the vdisk image.
The gpu btw which is a NVIDIA GT710 is using an edited dumped bios as per SpaceInvaderOne guide.
The physical disk has nvidia drivers in it and has the latest updates, along with Linuxmint updates
Same issue with me. UnRaid 6.9.0 stable, GPU is GT 710, Linuxmint VM, installed using vnc. After installation and reboot, it turns black nodisplay.
I have another LinuxmintVM booting from a physical disk - display fine.
Im working on a workaround and will post update here when successful