Wait.... from launch to splashscreen can take like 5 whole seconds, and it does not look like it is working, or that it has crashed. Until the steam "launch game" button changes back to green, then I know it's not going to launch.

It had Ran OOB for about 60 hours with my 980ti, with default settings (using proprietary drivers.) When I switched to 6900xt it would not even launch to menu. With "PROTON_USE_WINED3D=1 %command%" added, the menu would launch again. But would not launch into the actual 3d game with defaults. Dropped MSAA to disable, and it launched. Runs okay, but sometimes the FPS drops down, and it shows a 25/55 in the top left, presumably fps/ups counter. not sure.