If the black bar appears at the bottom of the screen in both Landscape (as illustrated) and when rotated to Portrait screen orientation, then you have demonstrated that the issue is software related. If the issue related to hardware, the black bar would remain static - as the screen is rotated between orientations.
Ordinarily, a forced-restart will usually resolve an isolated software issue:
Force restart iPad (models with Face ID or with Touch ID in the top button)
If your iPad doesn’t have the Home button, do the following:
- Press and quickly release the volume button nearest to the top button.
- Press and quickly release the volume button farthest from the top button.
- Press and hold the top button.
- When the Apple logo appears, release the top button.
Force restart iPad (models with the Home button)
Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
If the problem remains unresolved, check your selected Wallpaper image. Change the selected Wallpaper to an entirely different image:
Settings > Wallpaper > Choose a New Wallpaper
Having now chosen a different Wallpaper image, does the black bar still appear on the screen?