Just look at the screenshot on the RocketChat page. "Use on a production system is not recommended at this time" And looking at how buggy RocketChat is without federation I trust them not to use it.

Most of their features is just PR. For example they do advertise E2E while it has the same amount of warnings and not even a doc page https://docs.rocket.chat/guides/administration/administratio...

I wasn't defending Rocket.Chat's implementation. I haven't tried it myself.

Matrix is the practical solution, and Arathorn's sibling comment gracefully addressed my real criticism. Federation is absolutely possible on these applications, although tricky.