Well, just to rule it out, have you tried Windows? Like a neutered windows with defender disabled and such.

I’ve found that Linux can get rather fussy under high memory pressure. It works and doesn’t crash, but it also really bogs down anything high performance once the swapping begins.

It can also get fussy with Nvidia.

So I’m not saying Skyrim will run better on Windows, but it might be worth a shot.

I run CachyOS, yet I still keep Windows around for some other heavily modded games.