As of iOS 13.5, an external display by default mirrors what is on your iPad. This can lead to letter or pillar boxing when using some apps. While the list of apps that make full use of the external display is growing all the time (iMovie, Keynote, Netflix, Prime Video, Twitch, Procreate, Luma Fusion, MindNode, Shiftscreen and more support it today), not all apps will display in full screen on your external monitor. We fully expect more and more apps to support external video more dynamically over time.