Using Microsoft Teams on macOS, including installation, features, and compatibility
Possible workaround: Use the Microsoft Teams web version. It works faster, more smoothly and isn't affected by MacOS Big Sur!
Just to reiterate, the latest version of the Teams app works with Big Sur. I have installed on a number of Mac’s with no issues.
the web version is one answer but because of the feature gap between the web and desktop client, its worth perservering in my opinion.