> Use a federated secure protocol. Oh wait, there are none. Because if a problem appears you just can't fix it without breaking all federated clients. And then they will whine.

That's why you have to design your protocol with backwards compatibility and versioning in mind, ala XMPP. I'm not going to pretend its perfect, but it works pretty well 90% of the time. It does mean clients have to implement versioning and feature negotiation and not just blindly assume everything else supports all the features they do; convincing client authors to do this is the tricky part.

There are really two federated protocols, xmpp and matrix. Matrix is pretty young but looks good, they just added e2e encryption.

Check out the Riot client, web, android and ios. The apps are even native.

Plus, you don't have to show your phone nr.

Tox on mobile? Have you actually tried to use it? It drains your battery like crazy.

He didn't ask about that. He asked about a federated/distributed protocol that actually worked. Tox is one.