Are there any messaging apps...

[Norton Canes]

...that are fully encrypted, open source, not for profit, and also not hosted on AWS or Azure?

Asking for a friend.

[Zetetic]

Run an XMPP server, use OMEMO on your clients.

[Zetetic]

(Or there are a bunch of people hosting XMPP servers who might let you use theirs.)

[The Guppy]

Does Signal meet all the criteria? I'm not sure how it's hosted or how to find out.

[touchingcloth]

I believe Signal to meet those criteria, but it's not open source. Like Z says, you probably really ought to be running things on your own server if you want to be absolutely assured of privacy, but in the same way I trust Apple over Google I use Signal in preference to WhatsApp. I wouldn't run my various crime syndicates through either provider, but I'm slightly more confident that my data won't be mined through them.

[the Fallen]

Wickr has open source something or other.

[paruses]

Wickr has open source something or other.

Runs on AWS though doesn't it?