I'm using a QD-OLED monitor and love HDR for movies or tv shows but with gaming I have several gripes that don't make me enjoy HDR as much, funnily none of them caused by Linux.

A lot of games suffer from pretty terrible HDR implementations so it might just end up looking worse than SDR. Additionally, at least on this display tech, HDR is a trade-off between stable brightness (TrueBlack mode) or peak brightness (Peak mode). I find TB mode to not really pop enough to justify HDR, but peak mode to be too distracting for gaming since turning your camera can quickly change the overall brightness and make the image flicker.

I would say in theory HDR could be a huge increase in immersion for gaming but the tech and execution isn't really there for me yet.

HDR support on Linux though I find is in a pretty good spot if you're not opposed to setting a few env variables.

Not really. It can make the image pop a bit more, but that’s about it.

Absolutely. As long as your display is capable HDR and can output 600+ nits of brightness (1000+ preferred) and has high contrast (like an OLED display).

It doesn't require any effort, it's a checkbox in the display settings and a command line option in Steam. Assuming you're using GE-Proton10, you just put this in the command line parameters of the game that you want to play as HDR.

PROTON_ENABLE_WAYLAND=1 PROTON_ENABLE_HDR=1 %command%

You should pretty much always use the PROTON_ENABLE_WAYLAND flag*, the default is for wine to use xwindows and unless you're on a non-mainstream distro then you're using Wayland and so the display out put has to go through a compatibility layer (xwayland). This can introduce weird frame time jitter and hitching in some games that won't occur when using Wayland directly.

The game has to support HDR and there are some edge cases where the game won't detect that your machine is HDR capable so you can't enable the HDR option.

You can go through gamescope to have it work, but that is a bit more effort (mostly just installing gamescope and using 'gamescope %command%' (with some switches for options, like resolution, refresh rate, etc). This is a bit more effort and can have some performance overhead, but is still worth it imo.

*Using Wayland breaks Steam Input. You can still use a controller on games that support a controller, but if you use Steam Input to remap buttons or to play non-controller games with a controller then you'll have to wait on Valve to write Wayland support into the Steam Overlay.