This is resolved by using PROTON_USE_WINED3D11=1 in the launch options.
Same thing with wine, can't use DXVK.
For me (GTX 1080 TI, proprietary drivers) game enters black screen with music after the first banner and the song keeps playing. Can't do anything.
PROTON_USE_WINED3D11=1x1 2018-09
System Information:
https://gist.github.com/ryanmusante/e0789f11ca3adfa4442297ac0099461f
Game loads, settings screen allows changing video modes, etc.
Cutscenes, video and gameplay has invisible characters during movement.