Element for Android doesn’t support searching in encrypted channels and I think you can’t use E2EE in the browser at all(?), plus basically every other client has even more drawbacks when it comes to E2EE.
My team recently tried RocketChat, but E2EE is obviously an afterthought for that project as it has even more limitations than non-Element Matrix clients (no searching, no pinning, no file upload, no edit, etc.). Plus Jitsi integration seems to be buggy right now (at least on my Windows installation).
What else is out there that’s not on my radar? Is Matrix with Element really the best option right now? Is there no project that puts E2EE above all else?
Edit: Should be self-hostable and (FL)OSS.
https://wiki.xmpp.org/web/XMPP_E2E_Security
XMPP has omemo and pgp as e2ee.
I’ve hosted https://prosody.im/ before I went to matrix.
You will need to enable some of the extensions, if you want to have group chats, chat history and so on. But after initial configuration prosody will just work ™ and is absolutely lightweight.
The only reason I stopped using XMPP was, that no one uses it, which is sad, but I can’t do much about it.
Also one important bit is, that most clients are not e2ee by default and you need to enable that you only want to send encrypted messages and not plain text.