EDIT
This issue may be due to WebRTC being disabled. WebRTC is required for google meet, but also used for fingerprinting.
Recently I tried to join a google meet meeting in my hardened config firefox browser, and google meet didn't let me in at all. I was confused as hell. I could join only on my phone, but not any of my three computers I tested it on. I then went into a virtual machine with regular firefox(also linux), and the meeting works. The only conclusion I can draw is that google is so desperate for my data that they refuse to service me unless I give them this.
This post intends to inform people that issues with google products may be related to their valid wish for security, and the actions they have taken in pursuit of that. The post also intends to inform people of a solution. The two apps that I recommend are:
- Jitsi Meet: This is self hosted, but you can also make a meeting with jitsi's own servers. A excellent alternative to google meet, the only reason I didn't use it is that I had issues the day I needed to meet, and had to fall back to google meet instead.
- Jami: This is a distributed-network chat and video calling app which is open source and a GNU package. It does require an app, but is free and open source and will serve your purpose.****_________
Part 1
So first off I appreciate your "about:config" dump, that is helpful.
However, having ONLY that dump makes it difficult to actually diagnose your issue. It would be helpful to have an idea of what fails.
Second, you have "media.peerconnection.enabled" set to "false". That setting controls WebRTC. Google Meet uses WebRTC. If I set that value to false my Google Meet meetings fail to load, it just stays stuck at the joining meeting phase.
So maybe that's your culprit. Of course I would expect if you've had this set for a long time I would have expected it to fail for a long time. Also both alternatives you mentioned use WebRTC, so I would expect those to fail with that setting disabled.
Of course if it used to work with that disabled then it's possible Google Meet changed and had a fallback no longer in use or something else.
As an aside, I understand that WebRTC has (had?) issues leaking local IP addresses while connected to a VPN. So I understand why you might have it disabled.
The webrtc setting is probably it. IMO it's still google's fault for not providing a meaningful error message. It just stuck on the loading screen, assuring me that I would enter the meeting but I just didn't. I don't like webrtc because it can be used for fingerprinting, so I will probably use jami in the future
Part 2
Great. Your job is to take standard Firefox and switch one of these settings on at a time, testing Google meet until you find which one is the culprit. Good luck! 👍