No chat only? .... https://community.jitsi.org/t/chat-function-only/79067
As of 2020: end-to-end encryption optional and turned off as default, and marked as experimental...
Appears to be based on XMPP: https://community.jitsi.org/t/jitsi-users-is-jitsi-a-regular-xmpp-server/13211