Have you rebooted your system or tried selecting a previous kernel version upon boot to see if the problem remains?

Instead of guessing, looking at the log might help. Launch the game with PROTON_LOG=1 %command% set in "Set Launch Options" setting in the game properties. The log file will appear on your home directory.

I think mint has timeshift enabled by default. Try going back to when the games worked and figure out what change caused the gamss to break?

Thanks for the great and detailled report. Here's an upvote for you :)

Maybe you can try another prefix, like using Wine/ Proton 7.x instead of the current 8.x. Or try the GE-versions.

That's what helped me the most so far, but I didn't have many issues by now.

Also, those glitches sound like a faulty GPU or driver. Maybe try a live USB and launch a game from that with another distro like Fedora?

Have you checked out ProtonDB if the games work OOTB or require some tweaks?

DId your Nvidia drivers update recently? If yes try the older Nvidia driver

How do you handle which GPU is used in which game? I would guess you have an AMD iGPU, and a Nvidia GPU for games, right? Maybe something along those lines got updated?

Can you pinpoint what you did to your system before? Did you do a system update? Did you move game files around? Did you add any repositories trying to install something that also updated other dependencies, or alike?

Try using an older version of proton?

Did you move files to an NTFS shared drive? Proton + ntfs is flaky as all hell in my experience, and the problems are impossible to troubleshoot.

That must suck, I hope you get your answer man.