It's also the best distribution for jellyfin media player because it's trivially easy to get the jellyfin client to autostart in kde and it's not that hard to get it auto updating and rebooting nightly. This distro plus an intel n150 mini pc (aoostar n1 pro is decent) and a flir dongle and the flir remote is a big win.
HDR can be a hit-or-miss even on Windows though, thanks to the myriad combinations of monitors, cable versions and standards. So hard to give a definite answer besides "YMMV".
In my case though, it works fine without any hiccups. My main setup is a 7800XT, connected to an AOC CQ32G3SE using a DisplayPort 2.1 cable. HDR works fine both in Steam game mode as well as in desktop mode (KDE).
bazzite supports it I believe but I am not sure my n150 based mini pcs that I'm using on my tvs does. This was running on six your old tvs until this month when I bought a lg g5 for the basement. It looks great but I couldn't say if it looks the greatest it could look with HDR on or not... My previous tv frontend was a custom nixos setup that was a pain to maintain over the years. bazzite just works and the setup is simple for my needs (basically autologging in to kde and autostarting jellyfin media player in full screen plus a systemd timer to ensure the system updates and reboots overnight while I'm sleeping.
