HDR (and VRR) have been working for me for the past few months (Plasma 6, AMD), but I still keep Windows around for some games and yeah there’s no way I’m trying VR on Linux. I think I get noticeably worse performance on Linux as well, I think there’s some issue I need to fix with that.
It takes some fiddling, but I’ve been using HDR on Linux since Plasma 6 came out. If you don’t have an AMD GPU it would probably be really difficult to set up though.