It’s not fully featured but the remarkable series of epaper tablets are supposed to be pretty good and run a Linux fork. The supernote family run a version of Android that’s very stripped down and doesn’t require an account or an Internet connection ever.

I’ve had good success either using steam (proton is basically seamless and mostly runs by itself in the background without me having to do anything), or lutris for non-steam games

At least you didn’t spend $40k for the privilege