Matrix.org

Matrix is a decentralized communication protocol, similarly to XMPP. Although you can use a client and server of your choosing, as of writing there are fewer Matrix servers compared to XMPP which means less variety to choose from. The Matrix clients on the other hand are more modern, usable, and full-featured by default compared to most XMPP clients. The main server (matrix.org) is known for instances of censorship and political bias, which is why using it is not recommended, see servers. There are several clients to choose from, the main one is Element which works both on desktop or as a web client most Matrix servers run their own instance of. Alternative clients are Revolt which is mostly just a wrapper for Element, Nheko, Fractal, and there is also a plugin for WeeChat (beta).

Matrix Servers

See: https://www.hello-matrix.net/public_servers.php https://github.com/ara4n/matrixservers

Some notes on a selection of servers:

matrix.org Official server of the Matrix Foundation, you might want to avoid it due to its political bias.

chat.privacytools.io Has a CoC.