they use https://github.com/meetecho/janus-gateway as the webrtc backend, at least according to https://opentalk.eu/en/open-source-code-und-community. so the rust part is probably just for chat and signaling.
Sadly cadence seems to be dead: https://github.com/falkTX/Cadence
have used it, and its great. maybe it's a bit oldschool on first sight, but its a great, customizable project.
they use https://github.com/meetecho/janus-gateway as the webrtc backend, at least according to https://opentalk.eu/en/open-source-code-und-community. so the rust part is probably just for chat and signaling.