Did some testing on this on Linux, Arch + KDE 6 (wayland) + Nvidia GPU. It looks like DLSS works on Nvidia hardware. I didn't do formal benchmarks, but I didnt notice performance improvement. On my laptop it actually used roughly 10% more watts on the GPU while capped at 60fps. I don't think I could tell the difference on a blind test. So I'll use it anyway to do my part for hardware surveys.

Although this was Act 1, perhaps Act 3 will tell a different story.