Not bad, actually. We test with the Vive and the Index. If your distro has up to date drivers, it works well on both Nvidia (proprietary) and AMD. Nvidia is a little easier to set up, as there's only one real choice of driver, but AMD isn't bad either. Game support is obviously lesser than Windows, but a good number of games run well in Steam Play/Proton. That includes Beat Saber, which is probably the most popular VR game on the market.