I have the 3440x1440 Alienware with PopOS (gnome). Like others have said it doesnt support HDR, but the monitor still looks amazing. VRR works fine, which to me was more important (but possibly because I've never actually used HDR before, even on Windows PCs).
You can't miss what you never had! But now that I have OLED i could never go back to IPS/VA...
Big oof, long listed game for me and now dead before arrival.
Luckily I picked up FF14 already.