Download the latest Proton-TKG (Wine master) from ProtonUp-QT
Start the game you want to launch with it at least once
Search for it with protontricks and take note of the APPID: protontricks -s NAME
Set the registry entry: protontricks -c 'wine reg.exe add HKCU\\Software\\Wine\\Drivers /v Graphics /d x11,wayland' APPID
Set the launch arguments in Steam to: ENABLE_HDR_WSI=1 DXVK_HDR=1 DISPLAY= %command%
Switch the Proton version to the Proton-TKG you just downloaded
Enable HDR in KDE settings and launch the game
Some games crash on start, anti-cheat does not work and some games don't look right. So make sure to check that everything looks good once you're ingame.