I've been wondering about the paperwork side of "never met them, online only" collaborations. Contracts, sorting out the rights to use assets, and so on. Different parties might be in different countries, I'd imagine that brings some complications. Is there a common "this is how it's usually done" way of dealing with that?
I don't think there is a "usually done this way" method, there's likely tons of variations on agreements and contracts, that fit each project and the people working together on them. But there are many examples of contract templates online, for various situations, so you can look up some of those, and then adapt them to your needs (and probably consult a lawyer too if you can afford it.)
I don't have any legal education or experience myself, but I can usually understand everything a contract says, and have adapted them for my own uses of working with freelance artists, for example (paid work, not revenue share.)
And yes, I imagine having parties in several different countries will only complicate things (but only if things go south/get messy.) To be honest, I think legal contracts are only worth the paper they're printed on, unless you can actually afford the very high costs of litigating in court to enforce them. But contracts are still useful for making sure everyone is clear on their responsibilities, their rights, and what SHOULD happen when things work out and when they don't work out. Hopefully, you'll never have to go to court to enforce them.