I've personally used 4 encrypted communication apps, here are my thoughts:

Signal: huge downside that it required a phone number (not sure if it still does), and the centralized nature of it makes me very wary of it. It worked reliably when I did use it, but I no longer use it.

Matrix with Element: As others mentioned, it leaks meta data. It wasn't very reliable in my experience with encrypted group chats. Messages would constantly not be readable by other users in the chat, requiring frequent re-sending to finally get through. Overall I found it very frustrating to use.

XMPP: Experience can somewhat vary depending on the app used. With the Movim desktop front-end, I can sometimes have issues with encrypted messages not getting unencrypted (possibly just user error on my part), but with mobile apps like Conversations or Monocles, its been pretty much 100% reliable. Doesn't drain my battery either. Would recommend.

Deltachat: I've used this the least, but I really like it. Super easy to connect to friends and join a group chat, its all encrypted by default so no real chance of encountering an unencrypted message, very nice UI, is available on all platforms as one app, and has been 100% reliable with low battery drain. Highly recommend if you don't need to make voice calls (it can do texts, images, and supports voice/video files you can send and play within the app).