How to switch landscape to portrait Apple Air2 Ios 14.6?

To enable or disable Screen Rotation, you need to access the Control Centre. Swipe downwards from the top-right corner of the screen - then tap the Screen Rotation lock icon:

Rotate the screen on your iPad - Apple Support

If screen rotation proves to be problem with some Apps - and not others - you need to be aware that not all Apps are coded to operate in both Portrait and Landscape screen modes. Apps that have a fixed screen orientation will always appear in the orientation determined by the App Developer.

Most likely fix:

Pull down the Control Center from the upper right side of the screen.

Find an icon with a padlock encircled by an arrow.

Tap it to lock or unlock the rotation lock.

If that doesn't work for you, please explain where and how it goes wrong.