Huh, I was unaware that BG3 had a native Linux release, as it's not listed on the Steam store page. Turns out that they released it only for the Steam Deck. Strange
It was released at "end of life" for Larian patches for BG3, so I can imagine they didn't want to support any old Linux distro. I believe it is technically possible to run it on distros that are "similar enough"[0], but it's pretty pointless if you want to use any PC-only mods, etc.
So if you force it to run on your Linux desktop you don't get an experience commensurate with your hardware.