Gajim

Install

sudo apt install python-cryptography gajim gajim-omemo gajim-plugininstaller gajim-urlimagepreview 

This includes the OMEMO plugin (I didn't need to go here.)

Plugins

• gaim-plugininstaller: Make sure you have this so you can then easily add more plugins from within gajim.
• urlimagepreview: You want this - you might have to turn it on in the plugin settings

More download options (including Windows) are here.

Configure

Free server with secure group chat via OMEMO

You want to find a free XMPP server that is current enough to support OMEMO.

• Register on the website of this xmpp.social server.
• Add an account for it to Gajim, and connect.
• Create a new room! Set a password. Check members-only. You should be able to then turn on OMEMO!

Run your own server

TODO

XMPP mobile client

There's a mobile client that is supposedly capable of OMEMO. It's not free.  :-( But at least it's open source.

Incabable XMPP servers

On these (older?) servers, Gajim always says "group must be non-anonymous and member-only" even though I'd set it that way.

• https://www.kode.im/
• jabber.calyxinstitute.org