I've searched a bit about reverse prime, and there's an entry about it on arch wiki, however it seems it's only about X11 configuration and nothing about Wayland or anything else.
Well, at least with my current setup I can get VRR working on my main display without needing to disable my secondary one with my NVIDIA card.
You don't really need STL, just set gamescope as the launch parameter. I suggest checking
--help
to see what the flags do, but in general you'll wantgamescope -W <res width> -H <res height> -r <refresh rate> -f --force-grab-cursor --hdr-enabled -e -- %command%
. This works for me on TEKKEN 8, Helldivers 2 and Deep Rock Galactic.There are some issues, however. Some games might just freeze when running with gamescope (or gamescope with HDR flags), which is the case for me with Deep Rock, it'll freeze merely 20 seconds after it starts. Second issue is that, at least for me, the image will be incredibly dark and for some reason the SDR content brightness slider on Plasma settings will change the brightness of the HDR gamescope window, so I have to set it to 1000 to "fix" the brightness, but my desktop will be blown out with brightness.