Apparently since MacOS Big Sur thinks the screen is being recorded while the displaylink app/driver is active, the DRM and HDCP features block movie playback on all monitors including the MacBook Pro’s built in display. Movie playback from the Apple TV app returns to normal upon deactivating/quitting the displaylink app. Of course video files (and YouTube) that are not DRMed play back fine.
Apparently since MacOS Big Sur thinks the screen is being recorded while the displaylink app/driver is active, the DRM and HDCP features block movie playback on all monitors including the MacBook Pro’s built in display. Movie playback from the Apple TV app returns to normal upon deactivating/quitting the displaylink app. Of course video files (and YouTube) that are not DRMed play back fine.