How to enable WebRTC with Icecat?

I am trying to use the [Jitsi Meet](https://meet.jit.si/) web chat service with Icecat, but I am having problems (Icecat is derived from Firefox, but is more privacy/security focused). If I go to test.webrtc.org , it tells me that it can't access my webcam or microphone, despite the fact that I have given permissions in the preferences for that URL to access both. Does anyone know how I can troubleshoot this?