I recently found out about the Igalia software development collective, which has been going for something like 20 years now. They recently presented at the FOSSY 2023 conference. They don't do games, but if you are interested in learning more about governance for your project, and maybe some of the difficulties that can come up in a collective project, you might benefit from watching her presentation:
- Inside Igalia: scaling a co-op beyond 100 members (video: YouTube)
- Panel discussion (video: YouTube)