I deleted my only copy of Windows and reinstalled OpenBSD on my big PC. It's way better in almost every respect but I miss video games lol. I'll probably install Linux somewhere and boot that to play video games eventually but games on your native operating system are pretty convenient
Edit: thanks for all your recs, I am crashing from caffeine rn and have to log off lol, will check them all later
Doom is open-source ever since Carmack released the source code, so the various source ports floating around count as well, but I guess you already know this.