i just know that i used e2ee groupchats in matrix with multiple devices since sometime in 2017-2018 iirc. but that's not the point.
see, it's again a xmpp vs. matrix (vs. irc) discussion. that's bullshit. they all are far from perfect, all have different approaches (state sync vs. event streams vs. ...) and thus have slightly different use cases.
how about working together? i know for example the matrix irc bridges are not good, but that's a problem localized to the specific bridge software which is not good.
it's just so tiring.
@bonifartius @werwolf @chickfilla I disagree that they have different use cases. the current discussion is about their use as chats for humans, but what good is a chat protocol if the server implements it poorly, consumes insane amounts of resources thus making it unviable for most people to self-host without significant compromises and the most popular client being a buggy and shady mess. on the other hand, XMPP misses some features and has awful clients but it has fewer drawbacks otherwise imo
i self host matrix on crappy old hardware, it works fine except when joining very large rooms. matrix-synapse received good amounts of performance tuning over the years, there's dendrite in beta which isn't slow-GIL-python. the new sync-v3 protocol is supposed to fix the fuckups with joining large rooms and slow initial sync.
see, i'm not 100% happy with it either, but matrix still works massively better _for me_ than the alternatives. nobody i know cares about xmpp anymore. i long enough tried to have people care about it. everyone just switched to one of the siloed messengers. i could convince people to use matrix, because things like file transfers work reliably. some even don't use element but other clients and stuff still works. if xmpp is working better for you that's fine too. if irc is working better, that's also fine.
OMEMO is based on signal and OLM, i'd guess they could be made compatible, but i'm no cryptographer. maybe the bridges just need to support the respective key exchange messages. won't happen though as most people are still in the VS mindset (as they are for mastodon vs. pleroma vs. misskey vs. ...).
alas, people don't want good things people want to be right ;)