As can be seen in the following video:
The dropdown stays stuck open when Unity launches the game. This happens even with a non-modified dropdown that is plopped as a new UI object inside the canvas.
I tried a blank project, and the issue does not reproduce. I tried in a blank project, and the dropdown works. I tried researching a solution, but not too sure how to find one with this problem. Maybe someone here will have an idea or two.
The repo can be downloaded at https://github.com/DenisLabrecque/Warglobe if desired.