After some research, I found that I need to format my game so it can be played on computers without MonoGame installed. I think I found a solution, but I can't test it, because obviously I have MonoGame installed. I know its a big ask, but could someone maybe try this test (Not my Ludum Dare submission)?

https://speedysloth.itch.io/test-game?secret=GHfz5H02WIPTfNf0QaB2hdzj0