The current browser support check is too pessimistic and prevents some modern browsers from loading Microsoft Teams. For example, up-to-date Chrome on Ubuntu Linux is not considered a supported browser, even though changing the User-Agent string to Chrome on Windows allows Teams to load without any problems.

Please consider a) just letting the browser try to load Teams, b) using feature detection instead of the User-Agent string, or c) blacklisting known broken browsers instead of whitelisting if the User-Agent string is used.