Actually, I'm reminded of this story by @Gryphon from 2015, which features a chapter that details exactly how much the planet the main characters are visiting is in the pocket of a few capitalists/warlords - including, at the very end, the fact that they own baseball teams that are just straight-up named for them. The piece turned out less useful than I was expecting for this - that last part had stuck in my mind for some reason, but it's basically how Japanese baseball works, so it's not even that weird.
In any case, I'm an absolutely crap sports writer, but I can provide my usual service of wildly speculating back and forth with no real focus.
A question we need to answer is how exactly the tournament is constructed. Do we have clubs owned by the economic players or some sort of "national" teams representing individual asteroids? Undoubtedly it'd make more sense logistically to have local teams, but OTOH, I don't really see an amateur cup gaining much ground in the economic climate of the Belt - maybe as an internal OPA thing.
There's also the question of gravity, which isn't that much of an issue when dealing with Earth/Mars competitions as it is when gravity is a yes/no dichotomy. I don't even know how football would work in zero-g (handball or basketball OTOH might work better), let alone how to settle the difference when a team from Ceres with its 1/6g meets a team that's literally never trained down a well before.
You'd lose the ball in no time unless it was in some sort of cage, surely?
Think Blitzball from Final Fantasy X if you've ever played that, but without using arms - remember in football, contact is allowed with any part of your body except lower arms pretty much, unless you're the keeper in his box.
Also the goal would probably have to be set back in the centre of the cage rather than at the bottom if everyone is floating around
Glen did an interesting alternate football/rugby split in his Dominion of Southern America.
Hmm, all food for thought. I am willing to consider basketball if that seems more space-practicable, since I am also a fan of that (my commentary on either would be equally uninformed, don’t worry).
A hottake on what the space standard could be: centrifuges all set to generate the same gravity (my guess is Ceres-norm) in which case the game would essentially look like it was being played in a giant cylinder, with goals at each end.
if you want to make this more outre (and less book-accurate, since tbh it’s been a while since I read them) we could go with the idea I suggested of a uber rich bizarro-Belt divided into the equivalent of dozens of Monacos.