Matrix sucks. Server program written in Python with a very long configuration file. Every message sent is stored on server (like Discord). All Matrix clients suck, "flagship" client is an attempt to copy as much as Discord in a fast unstable way so there are bugs all over.
Slow as hell and most of the communities are just developer rooms. The "normal" ones are usually dead and when it is active its like being in a Discord chatroom. They advocate privacy yet censor creating or searching roms such as "porn" or "neet".
They claim to be the email of instant messaging yet you can't even set up a bridge to Discord/Slack/whatever from the app. You have to setup a Discord/Slack account and install more (nodejs/python) crap that may or may not work.

Yeah great instant messenger. Just use XMPP/Jabber or IRC.
At least it is actually stable and works properly.

Fuck off, IRC is still the best mass communications medium. Jabber is second to it. If you want encryption use Jabber with PGP or PGP encrypted emails. Matrix and Discord suck equally.