After trying all methods, from reddit and here, I got it working by using the heroic deb package and using HeroicBashLauncher. I added the game to steam using HeroicBashLauncher, then I just used this launch option PROTON_EAC_RUNTIME="/home/(replace this with ur user)/.steam/steam/steam...
But this results in an extremely distorted image (greyed out in the case of HDR PQ, and very oversaturated in the case of HDR scRGB), and the Steam Deck quick settings not even putting the little "HDR" badge next to the Brigthness setting, like it does in Steam games that are HDR ca...
For Linux desktop and Steam Deck modders you'll be pleased to know this release also now supports the Heroic Games Launcher. This means games installed via Heroic from GOG can now be modded via this Nexus Mods app, although in this case the REDmod for Cyberpunk 2077 ...