Yes, I'm having a DDoS attack these days, no idea why somebody would do that to my small server. I've deployed counter measures so the site is more or less usable, but the attack is still going on.
XMPP council (disclaimer: I'm a council member for the current term) asked me to some modifications and to re-propose, which I'm about to do. I couldn't find the time so far (cause I'm working on ton on stuffs), but will go back to it very soon.
And Libervia (disclaimer: I'm the lead dev). It also implements SFU including components (based on Galène), but I'm reworking design on this part.
Also note that Libervia is using a backend/frontends architecture with a D-Bus API, you can use it to make your own frontend with any language you like.
For a proof of concept, I've made a couple of years ago a "gateway" which was launching a local IMAP server in my XMPP client. This way you could use any MUA you like while taking profit of XMPP infrastructure (JID — XMPP identifier — are similar to email addresses) and its encryption (OMEMO can be used with that for instance). In other words, you could send messages from Thunderbird (or Gajim) to KMail by using only XMPP protocol (and thanks to IMAP Push, you got notifications immediately).