[pm3003]

Matrix comes to mind (Synapse server and whichever client you choose). It has good encryption and can be federated. Downside is that it gets heavy for old devices when you're in a lot of encrypted group chats.

XMPP is very efficient and delightfully simple to use and administrate. I never tried E2EC with it, but there are options on the clients, like OMEMO. It has limited federation.

The simplest server IMO is Openfire, but offers range from Lua-written Prosody to the extremely expensive Isode servers that can do complete federation, HF radio XMPP and probably coffee and pizzas too.

[tetrisgm]

I used to run a matrix instance years ago. I remember the account setup being super difficult for my family members. And the client was so basic. Is it different nowadays?

Omemo I heard of. from what I read it’s a solid alternative to Signal’s protocol. Is it easy to use? Is there something we can just run the server, spin up some users and have them easily dm each other?

[baobun]

ejabberd is a battle-tested XMPP server and they recently added a native Matrix protocol bridge module. So supposedly now you can have your users connecting over both networks seamlessly. Yet to actually try that.