SimpleX is currently the best one possible.

All the security of signal without needing a phone number.

Everything can be through tor. Contact link can be formed with a one time use code that you DM someone privately.

Anything more advanced and you're basically in internet dead drop territory. An encoded message on a pastebin through tor. Congratulations, you've entered pedophile/terrorist level security realm.

Briar, SimpleX, I2Pchat on desktop, maybe LXMF/Reticulum/Sideband over I2P if you want to get techy.

AFAIK simplex is the closest we have to perfect privacy.

https://briarproject.org/

Signal is far from perfect but its good enough for me.

SimpleX?

Tox would also be fantastic, but they need to improve their encryption and get it audited. Also, some nicer UIs in the various clients would be nice.

Session, Signal, Matrix, and more.

I think you don't want to know the real answer. It sounds like you want a phone app, but what you really have to do is flush your phone down the toilet and use a totally different approach. Also, there is absolutely no way to avoid difficult opsec. The communications technology is irrelevant since the greatest vulnerability in any security system is the people who use it. Do you think the private messenger software will free sessions with your therapist from spying? Guess again.

As the saying used to go, you're seeking a Star Trek solution to a Babylon 5 problem.

You need to define extreme operational security hoops.

For me, meeting a human in person and scanning a qr code or relying on an out of band scheme to do the same is a huge hoop.

I would still like to understand why Jami is never mentioned in these posts. I'm not aware of any technical or security objections, and the less I hear about Jami, the more concerned I become about using it.

jami

Your own xmpp server

Lot of people mentioning SimpleX but I can't imagine trying to make someone go online at the same time as me to start sending each other messages without being annoyed. It also relies on funding from the British state IIRC.

On the other hand XMPP is a W3C internet standard, the server is super lightweight, plenty of tools and bridges work with it. Movim uses it, which is like an encrypted Mastodon where you can selectively make a post public but otherwise gates everything behind a login. Also you can send messages on the main phone network with the paid Cheogram service, but I realize that an unencrypted SMS relay is not a priority for everyone. I think it's the bee's knees.

At first I read 'The Perfect Private Massager'

You want both, a completely anonymous AND completely private channel of communications? I mean, not to sound sarcastic, when you find one, please do share. There are no absolutes. For every technology, there exists or will soon exist, an equal, yet undoing technology. I have amended this to exclude most strong ciphers as pointed out by one of the Lemmies here.