I haven't really worked on it myself, but from what I understand, it has end-to-end encryption. If you self-host the servers, you can make it quite secure. It does have a metadata issue, but if you're self-hosting, that shouldn't be a problem. You can also use Tor.

But you can also do same with nostr by hosting your own relay. In fact new gift-wrap dm has better metadata protection.  

 Yeah it is ok i think too. It is heavier than other choices for self hosted communications though. Now matrix 2 is out. We will see soon about that