This is an old revision of the document!
If you don't like launching through steam.
Go to tty2 (or another tty), log in, go to game dir.
Run
DXVK_HDR=1 STEAM_MULTIPLE_XWAYLANDS=1 gamescope --hdr-enabled -O DP-1 -- proton run HorizonZeroDawn.exe
enjoy.