How to use Steam Input on Wayland games (including Proton ones)
Basically, you enable the Steam Beta and enable Steam to run through Steam Linux Runtime 3, and then launch Steam with -steamos3 at the end.
For Proton forks using the WINE Wayland driver, check out this guide on how to manually make Steam Input work.
Here are my launch arguments for Proton:PROTON_ENABLE_WAYLAND=1 PROTON_ENABLE_HDR=1 PROTON_USE_WOW64=1 %command%
(The video is footage of Helldivers 2 running through the WINE Wayland driver as you can see that HDR is enabled and the little window for the WINE system tray.)
I've tried to open an issue once before on PROTON-GE for an environment variable for this day, (Steam Input always worked, it would just not apply the profile of the game, only the Desktop.)