Looks like a deadlock. That shouldn't happen, but it can't work even after that bug is fixed. It's simply not possible for Proton to do what this program does. It *might* be possible in theory for Wine to do this for Win...
After using protontricks to install .net 4.7.1 the following log was generated. It doesn't crash, merely hang. [steam-382110.log](https://github.com/ValveSoftware/Proton/files/3993193/steam-382110.log)