I tried just yesterday with latest firefox and fedora, screen sharing didn't work out of the box. Only screen sharing by creating a virtual display worked, not sharing the current screen nor tab.

My screen share went from fine to low resolution all the time. Really annoying.

I have one thats purveying over apparently linux, mac, chrome, firefox... when you screenshare on multiple monitors (or workspaces) the screen stops updating.

it doesn't work "Your video isn't working. We couldn't access your camera."