I don’t know when the last time you used Wayland was but in Plasma 6 I wouldn’t say it “breaks other things.” Before Plasma 6 I had plenty of problems and stuck on X11 but now it’s great. So give it another try if you haven’t recently. Every issue I used to have with it a year ago is gone.
As for the obscure parameters, as of Plasma 6.1 all you have to do for games is add gamescope --hdr-enabled to the launch options for the necessary games. I don’t think that’s particularly difficult or obscure. You can also set up Steam itself to run in gamescope with --hdr-enabled and then every game will have it.
For HDR movies/TV/YouTube you can copy/paste the necessary options into your mpv.conf and then forget about it. It’s a one-time thing and then it works forever.
The biggest place HDR is missing is in Firefox, but Firefox doesn’t have HDR on Windows either so that’s not a Linux thing that’s a Firefox thing.
In my opinion, HDR on the desktop isn’t really there yet in general. Not just on Linux but on computers as a whole. HDR right now is really only for enthusiasts. The only monitors that properly support HDR1000 are $500+ for the entry level ones and $800+ for the decent ones. And you have to choose between miniLED with local dimming that don’t have enough zones yet or OLEDs that get burn-in after a year.