What platform/api could I use to split donations across multiple benefactors?

I've been looking across the internet, up, down, front, and back. No clue.

Let say two artists put their work together and want to add a donation banner on the webpage of their collaboration. For example, a singer shares their music with a video maker.
First, they agree on an arbitrary share for future donations. Like 50%/50% or 75%/25%, etc.
They may not know each other well, they may live in two separate continents.

Is there any platform or api allowing this?

• Once the share is agreed upon, an artist can not change it without the approval of both.
• The platform shouldn't be bound to a country (for example Stripe cannot accept international donations, unless the artists are in the US).
• I may be wishing for Santa Claus, but a privacy-friendly solution would be awesome.

Any idea appreciated, I've been drying my a$$ off for weeks on this one.