In case anyone is in doubt after reading your comment, I want to clarify that XMPP is "up to date" and has an active community and ecosystem of software projects, open-source and commercial.

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.

> Matrix.org which nobody seems to want to use and I’m not sure why

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.