I would like to suggest that you can play mini golf alone for the reason that you don’t necessarily need someone else to play and sometimes you have to wait a long time for someone to join the lobby. or there are people who join and a second before it starts they leave the lobby again (sometimes several times in a row). You can also play bowling alone, it would be great if you could do the same with Mini Golf.
You can start several game worlds (Minigolf, Ball Race, and Accelerate) in singleplayer via the main menu.
They can be found in the Game Worlds section on the main menu.