Spacetube is a group-to-group chat tool built on top of Matrix, a secure decentralised communication protocol.
Spacetube lets you open a channel to other groups from your chat platform, so you can talk to your own group and outside groups in the same way.
Get started or check out the github repo
Quick Start (simple web intro)
New to Matrix (intro to Matrix)
Used Matrix before (what spacetube does)
Talk on Matrix