Microsoft has begun to promote Microsoft 365 in full-screen pop-ups in Windows 10/11
However, for users, if they feel that this kind of pop-up window is too harassing, they can directly disable it in the settings, so as to avoid the system will continue to pop up the window after temporarily skipping it.
This full-screen pop-up window is titled to complete device settings, etc., and is actually promoting Microsoft products, including setting up Your Phone/Phone Link (after the latest update to the app), OneDrive, Windows Hello, OneDrive, Office 365, etc. and biometric verification.