Did you try setting your User Agent to Chrome? I have to use Teams for work. Under Firefox it has problems and missing features, setting my user agent to Chrome solves all of it. Highly uncompetitive if you ask me.
Also, pro tip: copying the most popular user-agent string gives you a bit of extra protection against fingerprinting. As of the time of writing, the most populated user-agent string is this: "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/114.0.0.0 Safari/537.36"
To me that sounds more like bad software dev/test procedures at MS than anything intentionally uncompetitive. For example, maybe they don’t keep their Firefox support up to date because not enough Teams users use Firefox to warrant the effort, but maybe Firefox is increasingly Chrome-compatible. Firefox is not popular enough for MS to intentionally cripple.
