Using Microsoft Teams on macOS, including installation, features, and compatibility
I turned them off.
Three dots next to my profile picture, locate the slider labeled "New Teams" and click it. Back on old teams, problem solved!
Seriously though, there is a "Why don't you want new Teams?" questionnaire when you do this. I selected "Other" and explained my frustrations with it to Microsoft.
Maybe if enough people can and will do this, they might get the idea that it was stupid to force the popups.