I was not able to get this to run through Steam Play (Proton 5.0-7). The game seems to load fine and the spectator window shows up. In the HMD the game does not start up. It is stuck on the "Next up" box in the grid loading area. The spectator window does accurately show rotations based off how my HMD is rotating, but I could not see hands / controllers when bringing my controllers in front of the HMD.