https://github.com/ricochet-im/ricochet

Every user is their own Tor onion service, so you get E2E encryption and no centralized servers. The whole thing hinges on the security of Tor itself which is probably a safe enough bet.

The problem though is that you’re still trusting the code. Nothing stops self hosted from rotting on you unless you look and read the code yourself.

Matrix is similar in many ways, and certainly younger, but also has a vastly different design at the protocol layer. It's more akin to a distributed JSON database/log, while XMPP is more focused on message routing and synchronization. Therefore each has different strengths/weaknesses for different use cases.

Despite these differences, both protocols indeed have IM apps and a whole lot of other software built on top of them.

Lots of people are using it (and probably more every day), but there are also some quite vocal haters. Of course it has its share of problems (availability of non-Electron clients and different servers among then), but many of them constantly improve as the ecosystem grows.