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 project

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.