The bug report is here: https://github.com/ValveSoftware/Proton/issues/4024 -- there has not been any activity in one year. Issue seems simple, just get a default binding for the game to work -- everything else seems to be in order, you can see the menu and options and even your own hands, you just cannot interact. But the most unnerving part of the experience is that you have no resource to try and fix yourself -- if you call the steam overlay to change the bindings, the Create Binding button does not work. The bindings screen shows an error message. The "choose another binding" button also does not work. I asked why it's this way on the steam bug report and got no response.