AMD is ideal but Nvidia is fine. Basically any game that would work on AMD will work on Nvidia (~~only exception I know of is the VR mode of Phasmophobia~~ edit: apparently this was fixed ~1yr ago). Gamepass still won't work though - blame Microsoft for that one.
That said, Nvidia has more of a performance hit when switching. Ancient Gameplays recently did a video comparing Nobara vs Windows 11, with both the RX 7900XTX and the RTX 4080 Super. These were his average results across 20 games:
RX 7900XTX: 1080p +2%, 1440p +0%, 4k -2.2%
RTX 4080S: 1080p -13.8%, 1440p -13%, 4k -10.2%
So your games will work. They just might run 10%-15% slower until you can snag an AMD card. If you're interested in fully committing, looks like most used 3080s are going for ~$500 on ebay, so you could probably get an AMD card and get most of your money back.
I also miss the gritty, dark, isolated atmosphere that KF1 had. I still had my fun with KF2, but when they introduced robot enemies, sci-fi weapons, and generally goofier cosmetics, it killed some of what made the games feel special