The XMPP Server

XMPP is a standard for instant messaging. The Extremely Corporate XMPP server runs on Prosody. There are many clients available. On Linux, use Gajim or Dino. On macOS or Windows, use Gajim. On android, use Conversations. On iOS, use Siskin.

Why use XMPP?

Because it lets you exchange the funny pictures and also talk and also

Conversations E2EE in MUC

Conversations has some difficulties with end to end encrypted messages in multi-user channels. The problem is that Conversations will not allow you to send messages unless you have exchanged fingerprints with all other participants. This poses a problem if a member of a group chat isn't often online. Unfortunately, Conversations' author seems unwilling to implement a strategy akin to Gajim's where OMEMO is used opportunistically when enabled (messages are sent to all participants with whom fingerprints have been exchanged, others are excluded).

How to into XMPP??

Once you have an account, you can be invited to the group chat