stuck while updating
device stuck while updating and not starting
iPhone 6s, iOS 13
If the update is stuck on verifying you might want to delete the update file and download it again
- Go to Settings > General > [Device name] Storage.
- Find the update in the list of apps.
- Tap the update, then tap Delete Update.
- Go to Settings > General > Software Update and download the latest update.
See this user tip that i have written about this subject for further reference
Updating/upgrading your iPhone - Apple Community