Do many distros use Wayland now? I use Kubuntu and it doesn't, so that probably explains why I never ran into any issue with that. Gamescope looks like some Wayland tool too from what I see. I don't have an HDR monitor either. Looks like good stuff, that I just never needed so never noticed it not working.
But to my knowledge, AMD GPUs pass through just fine to VMs? What was your problem with them?
I asked on the VFIO subreddit back then and was told AMD cards have a bug where you have to restart the PC to switch between host and VM (which makes it no better than dualbooting since you have to restart anyway), this was not the case on Nvidia.
So now that Nvidia has open source drivers and works on Wayland, what's the difference? Just gamescope?