Used to work great even on low specs servers, web UI was horrible. I am willing to install it again. No matrix, no slack, worried about Telegram.

This is one of those pieces of software that I've basically never run into issues with. XMPP itself is rather a moving target, so reviewing which modules are enabled from time to time is necessary, but other than that administering it is a breeze.

Erlang goodness.

Say what you will about XMPP, but it Just Works, supported by robust software like this.