Rocket.chat uses Matrix though, too. It’s not only Matrix but it makes use of Matrix federation among other things and they built their own Matrix server implementation in TypeScript last year
Correction they are actually moving away from the Matrix federation scheme in favor of their own federation mechanism to simplify the internal architecture (but they are still supporting Matrix financially apparently :)
Rocket.chat uses Matrix though, too. It’s not only Matrix but it makes use of Matrix federation among other things and they built their own Matrix server implementation in TypeScript last year
Correction they are actually moving away from the Matrix federation scheme in favor of their own federation mechanism to simplify the internal architecture (but they are still supporting Matrix financially apparently :)