In a previous discussion on HN about Jitsi, it was claimed that Firefox was missing some key aspect of the WebRTC standard that made sending video to multiple people more efficient; and that if a single person in the conference was using Firefox, the result would be a lot more CPU utilization for everyone.

So it "works" on Firefox, but the experience will be degraded when scaling up to more users. Hopefully FF can prioritize this feature now that the entire world needs high-quality video conferences on a regular basis.