Why Firefox? Chrome has a bigger market share to take. Edge is built on Chromium now so it should be a more familiar environment for Chrome users. Microsoft is in a position to compete with many of the integration features that make Chrome appealing to many users. Surely it makes more sense to target Chrome than Firefox.
Microsoft made me install Chrome just the other day. A company I work with decided to try MS Teams for communication and when I went there using Firefox, it simply refused to let me in and told me to get Chrome. They couldn't suggest Edge because I'm on Linux, so at least they did not require me to switch my OS.
edit: after accepting the invite and setting up an account I can use the product just fine in Firefox.
Yeah, for some inane reason direct links to Teams channels, chats, etc block you if you don't have a Chrome UA. In reality the only thing that actually needs Chrome is calls (which don't work on FF even with a Chrome UA).
