Change the compatibility version try experimental, or even I think the latest stable is 9.0. See if its runable under wine rather than proton. Try importing the game into lutris or heroic launcher you could have better luck but steam should be fine as I don’t think that’s the issue. You likely have to redownload the games rather than linking the drives due to file format types being different. I’ve used mint and several family members and gaming has been a breeze without much issues. It seems AMD is much more compatible than any Nvidia GPU. Drivers are better and updated more often under mesa than RTX. Let me see if cyberpunk is runable. Nothing should be an issue but a basic web search will tell a lot.

Edit: after research quickly the game has ran just fine since 2020 on steam since proton 5.0. Its buggy with Nvidia drivers but that was years ago. GoG store works under wine which is inside heroic launcher from software center in mint you can import the game but isn’t needed. You can try to use a custom steam command rather than using proton to launch inside steam. Proton is steams default compatibility layer but could need enable for all games. Go in settings check that box to enable for all games, retry. The game does work! Don’t give up. Also don’t aim the game to windows drive. Reinstall on your mint drive rather than just aiming the launcher. Windows does all it can to screw up anything that isn’t windows , verify installed files after download on mint drive and run the game. Perhaps I’ll add more later. Off to work. Hope this helps!!