I'm running Kubuntu 19.10 (fully updated) and Firefox 75.

Gmail allows you to make phone calls if you have a Google Voice account.

Prior to yesterday, each time I'd make a call, Firefox would prompt me, asking if I wanted to allow my microphone to be shared during the call.

Now, not only does Firefox not prompt me, if I click the lock-icon, it doesn't seem to realize that the phone call requires microphone sharing:

In the above screenshot, I've initiated a call, and I see no way to share my mic. This results in me being able to hear the other person, but they cannot hear me.

If I try the same thing in Chromium it works, and before yesterday, it worked in Firefox.

How can I get Firefox to prompt me for microphone sharing again?