As you know, Windows 10 allows you to define which applications or notification you want to see.

Well, until then Teams was not using Windows 10 notification when you had a message or activity.

You can now switch to Windows 10 notifications by accessing the Settings\Notifications option and select Windows for the notification style

After switching to Windows 10 notification, you will get Windows 10 notifications style; Teams will still show the red notification on top on the Teams icon in the systray