Direct LAN connections need the browser to reveal this device's LAN address. — it asks for the microphone once and releases it at once; nothing is recorded.
Until a page has held a camera or microphone permission, browsers put a
random <uuid>.local mDNS name in every ICE candidate
instead of this device's LAN address. This Wi-Fi does not resolve those
names, so the other device drops every candidate it is sent and the
connection never forms.
Firefox asks every time unless you tick "Remember this decision" in the prompt.