The Bonfire team are an ActivityPub powered set of software and servers. They’re currently going through a crowd fundraise, and just met their first “maintenance” goal and are fully funded.
This article announces that and then goes into detail on their first stretch goal, which is federated groups.
The article is excellent in going through different types of communities and their needs. A very good read to learn from related to a variety of collaborative and/or private use cases we’ve discussed.