I managed to make the keyboard extension re-appear by switching the affected apps' language back and forth. For example if your preferred app language is English, then you can go to Settings > (the affected app) > Preferred Language > switch to another language > launch the app > go to settings again > switch the language back to English.

My solution: Create screenshots with iPhone SE simulator with iOS 17. Download iPhone 8 Plus simulator with iOS 16.4 Drag the screenshots into the iPhone 8 Plus simulator. Open the screenshots with Photos app in the simulator. Screenshot the screenshots.