Random broken things and weird tinkering to get some things working. And even when they work, not quite as good as windows.

Most overlays don't work because they are tied to windows specific windows capture things. On KDE wayland, the default "view desktop" from SteamVR doesnt even work.

But if youre looking for some very chill things, it's generally passable. I've been playing beat saber, which is fast paced (at least for the hand tracking) and proton handles it perfectly. From what I can tell, proton can handle VR games just fine, there's just some work to clean up the SteamVR interface in general.

I'm still delusionally hoping that the Valve Deckard is shipping soon and that when that drops, there will be a big SteamVR 3 linux update (kinda like how SteamOS 3 came out with the steam deck), and the headset will run linux itself so naturally they will have to ship all their linux VR improvements, and we'll see linux VR suddenly become mega viable.

tl;dr - working, depending on your level of tolerance for slight jank, and what games you want to play.