Rocket.Chat adding support for #XMPP is very good news.
„[XMPP] is self-hosted, air-gappable, open, and auditable, and it is light enough to hold up on constrained tactical networks. Those qualities are why it has stayed in service for two decades. The protocol is mature and trusted. […] It is usually the client software sitting on top of XMPP, not the protocol itself, that has aged.“
https://www.rocket.chat/blog/rocket-chat-8-7-brings-xmpp-interoperability-for-coalition-operations