After starting the scenario, at the map/briefing screen I am unable to do anything but move the map by placing the mouse cursor at the edges of the screen. Clicking buttons doesn't do anything (I can't even go back to the menu) and using the mouse on the map doesn't work either. I tried using my keyboard but no luck there either.
I am using the main/stable branch of the game.

Possibly related to change note "Disabled user input for the intro, so players don't accidentally exit the helicopter."?