I wish there was a way to do local peer discovery with WebRTC. Right now both endpoints need an active Internet connection and a shared identifier (in this case a special URL) in order to find each other. Can't do offline local sharing.
It uses mDNS for discovery. You can only do one browser though.
I don’t see a path forward on browser/browser that is obvious. It would make it so easy to fingerprint if you could set your mDNS hostname in JS
It could be done with a browser-owned dialog to select peers instead of exposing all local peers to the web by default. Similar to the web MIDI API or others that expose local devices only with explicit user permission for the specific device.
I once did it by copying messages from textarea's back and forth.