So I set up a XMPP server in my homelab this weekend to see how the ecosystem has evolved since the last time I used it. Only took me a few hours.
It seems like it has pretty much everything we'd expect from IM these days? E2EE with forward secrecy, group chats, message archives, reactions, file uploads, audio messages, voice and video calling, location sharing, etc. etc. It's even federated!
Why are we sleeping on this tech? Is there some unmitigated downside I haven't discovered yet?
Speaking from a #Jabber/#XMPP fanperson perspective, the downsides are:
1. No good client with A/V calls for Windows. #Gajim by @gajim is on the MS store and is good, but doesn't have A/V calls, #Dino by @dino is also good, has A/V calls, but only has outdated Windows installers somewhere on the net. There is #Movim by @movim, but web clients are not everyones cup of tea. Problem can and will be solved, but atm. it is a drawback. Maybe #Kaidan by @kaidan will solve that.
2. Because of the long history of Jabber (since 1999!), and huge advancements in cryptography, encryption in XMPP has many options. So far, so good, but most clients are still on #OMEMO 1, which has some problems, and only few clients already have OMEMO 2 (#Kaidan by @kaidan, #Libervia by @Goffi, soon‽ also #Conversations_im by @daniel, #ConverseJS by @jcbrand and #JabberEl by @[email protected]). And there is no standard way to move decrypted message from an old device to a new one!
3. A/V calls typically work great for one-to-one calls, if network, TURN server etc. are working correctly. But multi-party calls are "not there yet", esp. for groups > ≈ 4 people. Both #Movim by @movim and #Libervia by @Goffi have it on their roadmap, and I'm optimistic, that it will work well later this year or the next.
That's the three downsides from my PoV, but Jabber is still my favourite chat.
@debacle @gnemmi @smn @movim Hey, SFU (big conferences) is not just on the roadmap, there is a working prototype for nearly 2 years now (based on the excellent Galène), with corresponding specs in XSF /inbox. Well was working actually, broken right now due to big changes in web frontend, but should be back soon.
Justin Fitzsimmons
Gonzalo Nemmi 
Debacle
Goffi