Shameless plug: As an alternative to solutions like WebTorrent, if you do need to rely on a signaling server but don't want to send your signaling data (ICE candidates containing IP addresses in this case) unencrypted over a cloud service like Firebase, it's possible to use an end-to-end encrypted protocol for this use case: https://saltyrtc.org/ The good thing about this protocol is that you don't need to trust the server.

(Of course it would be nice if we could just send an UDP broadcast or announce the device via mDNS/Avahi, but browsers do not allow direct network socket access, due to reasons™.)