They support meetings in Firefox so it's a bit weird why they would block calls... They're effectively the same thing
Additionally, if you change your userAgent to be Chrome things are working pretty good in Firefox as far as I've tried it (not too extensively)
I've used: User Agent Switcher
Successfully using;
teams.microsoft.com
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36