How do I remove iOS 16 from my iPad?

Rolling-back to an earlier version of iOS/iPadOS is not possible.

All System Updates are digitally signed by Apple - and can only be installed whilst the digital signatures remain valid. After release of a new iOS/iPadOS version, the immediately preceding version continues to be digitally signed by Apple - however, usually within a few days, Apple will revoke the digital certificate with which the earlier version is signed.

If Apps no longer work properly following update to a more recent version of the OS, you’ll need to seek assistance from the related App Developer - as only they can resolve issues with their App.

How to contact an app developer - Apple Support

Perhaps consider that iOS/iPadOS updates include both functional and essential security updates. Restoring an earlier version of the OS would undermine the security of your device and your personal data. 

For information, Apple do invite submission of comments via its Product Feedback portal. For iPad and iPadOS:

Feedback - iPad - Apple

You can't. Downgrading is only possible when going from a beta to the last release or otherwise noted.

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