I have just submitted the below via the Feedback feature in Teams (ironically, when I opened Teams, I received 5 popups...).
I suggest that others provide similar feedback via the Teams Feedback feature in the ... > Help menu of Teams. Make sure to say that the feedback goes to the PRODUCT MANAGER, else you will end up dealing with someone in the support space that can't get anything changed because they are too low down the food chain.
Please view the thread below. Everyone hates all these annoying popups in Teams and Office products. We have to be given a way, as IT staff, to block these annoying popups. It interrupts users, is inefficient, and nobody wants to see them in ANY of the organisations I support. It comes across as 'needy' and constantly needing validation. Your changes are too often and people are getting very frustrated. I am sure that my concerns will be dismissed, as if we aren't in Redmond nobody seems to care. The URL below has FIVE PAGES of people complaining about this. Please take notice and make changes by escalating this to the PRODUCT MANAGERS, not just someone in support that is not empowered to make changes. https://answers.microsoft.com/en-us/msteams/forum/all/teams-disable-new-feature-popups/6cfa8e35-b06b-44d0-80fc-e40eb68624e0?page=5