I use teams on Firefox and haven’t encountered any issues. Admittedly I only use it occasionally, as I do mainly use the desktop app.
I think they added some compatibility in the past year or so but I had issues detecting my microphone on Linux just 2 weeks ago. I’ve had some smaller ecommerce sites fail to load properly on Firefox/Librewolf, Red Hat’s Training website doesn’t work on Firefox, and also some features on apps like Google Meet and Miro are unavailable. It’s nothing that makes firefox unusable, and I can always open up ungoogled chromium when needed, but it is a serious issue for browser diversity and competition that the web has defaulted to chrome now.