I like signal, but I prefer free software and I mean no company involved.
Now XMPP it is old and has RFC (it is officially protocol of internet). Almost all clients of recent decade supports omemo encryption.
There are more solutions if you want to check; if you write a review even better, send me the link :)
deltachat (this works with imap)
simplex chat (https://simplex.chat/)
wire (https://wire.com/en/)
jami (ex-ring)
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