Tell me, what kind of payment processor do you know that will work in many countries? I think this information will be useful for the project.
I do not think that such exists. You can use bank transfer. But this is an inconvenient, expensive and strictly controlled payment method. Using cryptocurrency in such a context looks very useful.
Even bank transfer do not work in all the countries. It is very expencive and there are a lot of intrmediaris. But besides there are a lot of sunction and banks do not work with some countries.