Try installing a User Agent switcher into your browsers and then fake your browser ID. FF works fine with Teams, Exchange and M365 - I have been an IT consultant installing or using all of that lot for over two decades.

I too have a favourite browser. It used to be FF up to about 15 years ago (v2 or so) then Google were cool and I went all in on Chrome. I then went Chromium. I actually started out with telnet but that’s another story.

A couple of months ago I finally dumped Chromium and co and went back to FF. Biggest win for me was a slightly less opinionated SSL experience. That needs some explaining:

I run a lot of IT and that means a lot of SSL certs. Mostly I use Lets Encrypt if I can as well as the usual suspects. Sometimes a site does not need SSL at all. Googles browsers are very VERY opinionated about this: “Thou shall not use thy browser password manager with self signed SSL certs”. FF has a slightly less opinionated “Thou canst TOFU and thy password manager will work”. I spend a lot of time pissing around with uploading CA certs to group policy objects and copying them to /usr/local/share/ca-certificates and getting the machines to trust them. On Arch we use /etc/ca-certifictes etc and so on and so forth. I also have to deal with Teams - FF works better now than Cr browsers

I’ve returned to FF after a very long time and I don’t regret it at all. I run Arch actually!