Only got it to start with proton 4.2-9. Videos do not play, but the sound can be heard. Error message from OP still pops up, but upon clicking "OK" the game starts. Fullscreen can be enabled with ALT+ENTER, although not all resolutions are accepted.
Ingame, the cursor cannot be used to "circle in my units", as they have a wierd offset.
Sadly not playable like this.
Try on proton 10.0-3
proton 10.0-3x1 2025-11proton 4.2-9x1 2025-08PROTON_FORCE_LARGE_ADDRESS_AWARE=0x1 2020-06
Compatibility Report
System Information
I confirm:
Symptoms
No Start:
No Video:
Game Error Popup:


gnome-shell panel is visible (with both dxvk and wined3d):
Cursor disappears/flashing (with both dxvk and wined3d):
Reproduction
Logs:
steam-2710_PROTON_FORCE_LARGE_ADDRESS_AWARE=0.log
steam-2710_after_install_wmp9.log
wined3d + gnome + xorg session:
wined3d + gnome + wayland session:
dxvk + gnome + xorg session:
Notes: