NullReferenceException at startup (endless Loading screen)

[TamaMcGlinn]

When starting up Geographical Adventures on some machines, the black screen with white text "Loading" remains and nothing happens.

Looking in the console from which I started it; I see the same error over and over again;

NullReferenceException: Object reference not set to an instance of an object
  at GameController.get_CurrentState () [0x00005] in <f59034706e284a7b888fee3d0080320a>:0 
  at GameController.IsState (GameState state) [0x00000] in <f59034706e284a7b888fee3d0080320a>:0 
  at MainMenu.LateUpdate () [0x00000] in <f59034706e284a7b888fee3d0080320a>:0 

I'm still debugging, unfortunately I cannot say for sure which exact version of GeoAdventures I'm using, but since I installed this from master in June 2024 and there have been no substantial commits since then, it shouldn't matter. I'm on Ubuntu 22.04.5 LTS with Wayland windowing system, GNOME 42.9.