I agree. IMHO the best variant is then to use something that is truely free. Like XMPP. There are a lot of servers and many clients to chose from and I can strongly recommend converse.js as a web client. It supports different ways of end to end encryption but I would recommend OMEMO which is basically the same encryption idea that you find in Signal. Source: over 1 year ago

Hello, I recently started exploring xmpp, with snikket app and conversejs.org. Source: over 1 year ago

It is Converse.js (https://conversejs.org/) packaged into a one-click install for openfire (from the web admin). So, one-click install for an xmpp web client. Source: over 1 year ago

My choice, because it's the stack I know very well, would be Prosody ( https://prosody.im/ - I'm one of the devs) and a web client such as Converse.js ( https://conversejs.org/ ). XMPP is highly extensible, Prosody is highly modular, which make them a good foundation for building on top of. That said, the right stack is generally the one that matches your requirements, and (if this isn't primarily a learning... - Source: Hacker News / about 2 years ago

Tried to register with conversejs.org today and got an error "your IP is not whitelisted". Source: over 2 years ago

Sending notifications is just a tip of what developers can take advantage of. Telegram also offers tdlib (Telegram Database Library), a cross-platform, fully functional Telegram client which allows anyone to build their own custom messaging apps operating in the Telegram cloud. - Source: dev.to / over 2 years ago