Download Flatseal from the Discover Store. Go to the itch app in Flatseal, scroll down to Environment find the says PATH=... and replace the whole line with this
PATH=/app/bin:/usr/bin:/usr/lib/extensions/vulkan/gamescope/bin;"/home/deck/.local/share/Steam/steamapps/common/Proton -
Experimental/files/bin/" you can replace Proton - Experimental whatever Proton version you are using.