Janus is used by the PiKVM project for WebRTC streaming. I found it arcane to configure and never got it to work over Tailscale (https://janus.discourse.group/t/failing-to-establish-webrtc-...).
media.peerconnection.ice.obfuscate_host_addresses = false
https://webrtc.github.io/samples/src/content/peerconnection/...
If you do not get any valid candidates, then it is most likely a misconfiguration of your browser, vpn, firewall or network. Unfortunately this is most likely not a Janus thing, but I would need more information to know for sure.