Staring the game without any options (except PROTON_LOG=1) causes no UI to load and the steam logs indicate that ERROR: ld.so: object '/home/flexperto/.steam/ubuntu12_32/gameoverlayrenderer.so' from LD_PRELOAD cannot be preloaded (wrong ELF class: ELFCLASS32): ignored..

Any combination with PROTON_USE_WINED3D=1 PROTON_NO_D3D11=1 PROTON_NO_ESYNC=1 PROTON_NO_ESYNC=1 (i.e. 15 tests, with 1 to all arguments) causes in-game errors to be created. Blackbox-reviewing of the logs doesn't indicate further debugging approaches to the author, so the game doesn't seem to work on my system.