Jack Dorsey just Announced Bitchat(A secure, decentralized, peer-to-peer messaging app for iOS and macOS that works over Bluetooth mesh networks) Licensed Under Public Domain.
Getting people to move off Messenger or even WhatsApp is tricky enough already for to interview and resistance to change. But even when you can coax them to move, you then often end up in a debate about where to move to. Signal, Briar, Viber, whatever proprietary thing Apple is currently pushing, or the thousands of other options/apps. I guess we can just add this one to that long list.
None of them cross the line yet to be “good enough” in practice for all the use cases of an offline messenger. Briar is probably the best, but not useful if even one of your group is on iOS.
That's a good point. And to add to it, I've tried using Briar as an emergency option if there's no Internet. And there seems to be a massive flaw in that scenario: you need the Internet to authenticate yourself on the app. So if there's no Internet it's useless. I just tried switching off WiFi and 5G on my phone and yup, can't log in, so can't use it.