The game starts in Fullscreen, but the mouse cursor is not centered. In order to click something, you must click to the side of the icon. My fix was switching to "Windowed" and then back to "fullscreen". I am running Bazzite. So, for my specific Distro, once I went into "windowed" mode, I had to double click the title bar of the Flight Sim application to get it to recenter. Once it was recentered, I could then revert back to fullscreen and the mouse is aligned properly.