nostr can do this. relays are lightweight enough to run on Android devices, Citrine ships one with a nice UI even. It's not p2p or anything but it works well enough to preserve your own note history and there a plans to extend its functionality beyond that.
For this to be long-term sustainable though, it needs to be implemented in such a way that non-tech-savvy folks can also participate very easily, without needing to learn anything about P2P, relays, decentralized or edge computing, etc.
https://github.com/greenart7c3/Citrine