Apple has launched a new pop-up to allow users to turn on or off personalized ads within the App Store and other Apple apps. The pop up is only shown when users enter the App Store on iOS 15.
App Store Personalized Ads Pop Up
The pop up seems to be completely server side, rather than built into the beta release, as it did not show devices as they were updated on the day the new iOS 15 beta was released. AppleInsider can confirm it currently does not happen on iOS 14.