iOS 12 compatibility

[a-casual]

Would it be possible to maintain iOS 12 compatibility?

It does not look like the app requires anything specific to the new OS, and Apple disallowed upgrade to iOS 13 on older iPads

[superk589]

The native dark mode support and CoreData background syncing with CloudKit are specific to only iOS 13.
It's possible to maintain iOS 12 compatibility. But since this app is not released on the App Store and there are not many users running an old OS. Then I decide to drop the old OS support and focus on the core features to make it a delicate tool.
Besides, if you are a developer, you can just fork the repo and modify the source code to make it compatible with iOS 12.