I'm very glad that @Chocobozzz is working on PeerTube, a federated video hosting platform. I think there is a lot of, if I may put it, thirst, for a photo sharing platform too. With those superficial differences between how Mastodon works and how Instagram works.
And I mean, you could just fork Mastodon and modify the UI. Or you could build on top of ActivityPub from scratch, like PeerTube does. The possibilities are fascinating. All within one network.
The social network of the future: No ads, no corporate surveillance, ethical design, and decentralization! Own your data with Mastodon!