I have three, 99% of the times it works well but games tend to have a problem with it sometimes.
Either way, it is fixed now. If there's a user out there with a similar problem: Try to make it run in a window with a border. I got it working with Wayland, changed the settings, switched back to X.
Thanks for your reply! The game does properly work when I run GNOME with Wayland and I just played the game for a bit without any issues. I'd check with X in windowed mode but I don't have time to do that right now.
I have a multimonitor setup, maybe that is why it was acting weird.
Whenever I try to click anywhere on the user interface in the starting screen (such as "options" or the little planet you're supposed to click on to play), it only interacts with whatever is behind the Besiege window. Mousing over the interface does give the appropiate response, but left- or...