The game seems to use Vuplex WebView. Launching the demo with the environment variable PROTON_SET_GAME_DRIVE=1 prevents the crash. Completed the Ashkelon campaign mission with it set.
@cooltyp100 Thank you for the investigation and for posting the results! I'm adding gamedrive for both the demo and the appid for the final game, under the assumption that the full game will need this too.
Compatibility Report
System Information
I confirm:
steam-3209830.log
Symptoms
The demo for the game crashes when starting any of the campaigns.
Reproduction