Fair call. Other people have commented on issues with matrix so I won’t dilute the thread by repeating that. I mentioned session as an alternative because it meet the criteria set for the poster by being decentralised. It’s also E2EE and routes messages via onion so encourages anonymity.

There are a heap of comparisons available on the different encrypted messaging apps, but they all put different weight on various features which can skew perspectives. Here’s one for consideration:

https://www.securemessagingapps.com/

Personally I use signal, matrix and session, and think they all satisfy the requirements for my threat model.