it appears Jitsi is a link embedder

It isn't clear at all how you came to that conclusion. Jitsi is a VoIP + IM solution.

If there are some FOSS options

There are loads of them. I would be using Asterisk for VoIP and probably Prosody for IM. If you are looking for a Perl answer then DJabberd is still available but (unfortunately) it has had no active development for a long time.

Update: although DJabberd hasn't seen a release in a decade there actually has been some more recent activity over on the github repo so it might not be quite such bad news on that front as it first appeared.