How to fix IPad Pro 10.5 inch. IOS 17.6. Bright black screen of death?

At the time of writing, iPadOS 17.5.1 is current.

If you have installed a beta version of iPadOS, as your description would suggest, you should have every expectation of encountering bugs or issues - which may, in extremis, render your device unusable. You should attempt to reinstall the current production version of iPadOS:

How to uninstall iOS beta software - Apple Support

If you are unable to resolve the problem yourself, you might be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page.

Alternatively, you can initiate and manage your support cases from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:

https://apps.apple.com/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to offer assistance:

Genius Bar Reservation and Apple Support Options - Apple

Be aware that Apple generally will not provide assistance for devices with beta software currently installed - and as such your options may be very limited.