I can’t find either Cromite or Ironfox on F-Droid…what am I missing ?

Prosody (XMPP server). Setup takes an hour at most even if you have never worked with Lua. Easy to interact with (it has a built-in shell), easy on system resources, and easy-to-understand config. Support for groups, E2EE, attachments including videos and voice recordings, among others.

I understand that BSD see closed source as something cool

‘You understand’? Where did you get that idea?

The argument is not, and was never, that closed source is cool. The argument is that strong copyleft, while based on a noble goal, ends up hindering development: Here’s OpenBSD’s take on it. (CTRL+F for GPL).