The game need for now heavy work to arrive there :

• With vanilla proton, dll in part/core are not loaded, linking them in the main directory is necessary
• .Net is necessary, dotnet472 did not work for me, but dotnet461 is ok

With that, the game is loading and you can see the loading screen. Next it crashes on a video (ASF format) unreadable by GStreamer. Installing wmp11 with protontricks allowed me to reach the menu.

For now I have heavy graphical glitches, I keep digging.