Hello,
Im very surprised to see that it's almost abandonned since 2016 As there are multiple others messaging apps, I hugely prefer/recommand xmpp. Daniel Gulsche did a horrific work about his good client conversations.im and quicksy.im into android. The community thanks him.
The difference between conv' and quicksy : the first one uses login/password. The second one uses cell phone number. That's all. Sometimes it happens that Conv and Quicksy are free few days on playstore. Always, on fdroid. Others good/modern ones are monal for iOS, beagle for mac, and dino for nux/unix/bsd.
To be clear I learned about xmpp in...2022. I hugely regret that “late”, as I was using especially SMS/emails until 2020. No “smartphone app” for over two decades (and not more now). But for me, as a very attached person into the “federated” and uncentralized criteria of the internet and online services : I discovered xmpp by comparison with matrix/element protocols. And have to say I have used a bit more than a year the matrix/element one, not that bad, but finally... not that convenient.
XMPP is a bit for instant messaging, what are emails : – decentralized, federated, as for opened-SIP (for little ToIP providers) ; means if a servers goes unavailable, it doesnt avoid other's servers to communicate (unlike whapp/telegram/signal/etc) – not that hard to setup : username, password, that's it ; even quicksy proposes to use phone number instead (a bit like big messaging tools) – multiplatform : unlike big messaging apps, xmpp clients are available on windows, macos, linux, unix, iOS, android, haiku, BSD, and pure linux for mobiles – communications are encrypted with OMEMO protocol, inspired from signal. PGP could be used too. – voice/video communication works with modern clients – files transfers works easily, too – doesnt belongs to big companies whom do monney on user's data.
XMPP and SIP are exactly what email has been powered for : decentralized, multiplatform, as a reliable standard for internet communication. No, “big four” doesn't play such game.
...SIP is not that far of that. For my close relatives, friends and family, we setup those both protocols for a simple thing : we dont want to depend of a single server/company. And of only 1 protocol.