We currently have the Matrix protocol, with client applications such as Element supporting it. We also have XMPP as another option. Generally more modern than IRC, these platforms are primarily developed as FOSS software. This makes it less likely for developers to impact their users negatively. However, despite these advantages, these platforms lack the refined user experience (addictiveness and stickiness) that... Source: about 1 year ago

That's essentially what we had with Jabber/XMPP [0] and OTR [1]. Since the encryption happened client-side, it would also work across networks. There was a time when Google chat, Facebook Messengers and other high profile chat networks could all interconnect through it. [0] https://xmpp.org/. - Source: Hacker News / about 1 year ago

Xmpp there's loads of clients for it no phone number needed https://xmpp.org/ pick a server loads have sign up via the client. Source: over 1 year ago

I present to you a MUC I've created on the XMPP (also informally known as Jabber) network. I've put some thought into which network would be best fit and decided that, while IRC is an excellent way to chat, there is an apparent lack of mobile support and perhaps lacks the ability to choose a server of your choice. Furthermore, I've concluded for many years that Matrix isn't a good choice for multiple concerning... Source: almost 2 years ago

Interoperability of messaging used to be the case, and the underlying tech is there. At one point, Messages, AOL Instant Messenger, Facebook, and Google Talk / Hangouts / Voice all supported exchanging messages via the IETF XMPP (Jabber) messaging standard. Sometime in the mid 2010s, the services started removing XMPP support, presumably in an order to differentiate their platforms and lock people in. Source: almost 2 years ago

Use https://bridgefy.me for offline communication. Source: over 1 year ago

Have a look at https://bridgefy.me/, this may be interesting to you. Source: over 1 year ago

5. There's another company called Bridgefy https://bridgefy.me/ that built a chat app used in some of the Hong Kong protests. - Source: Hacker News / almost 2 years ago

Bridgefy is designed to work on local Bluetooth (max about 100m) during natural disasters, a protest, at large events, at schools, etc. It will create a mesh network, so one or more other peers can help transmit messages further. See https://bridgefy.me/. Source: about 2 years ago

How about offline P2P mesh bluebottle chat? Check out this one used by protestors https://bridgefy.me/. Source: over 2 years ago