I’m new to Android development with the current Android Studio and supporting library’s support Android 9 Development, looking at getting started in Android development for an app that will run on an industrial control panel running Android 9 and no higher. Anything I should be worried about?
It has always been (and probably always will) possible to do that, see: Android Developers > Docs > Guides > Support different platform versions > Java
Obviously, going back too far is a security risk. But seems you’re going for in-house, so it’s perfectly fine. Just keep testing your app with the built-in emulator (obviously, loading an Android 9 image).
If you only need Android 9, you only need to download SDK packages available for download for Android 9 (API level 28) from the SDK Manager, in the SDK Platforms tab of your Android Studio to develop your app.
Reference: Android Developers > Android Studio > What’s new > SDK Platform release notes