I got my app into Google Play's app store but I also got this warning:
Your app currently targets API level 14 and must target at least API level 26 to ensure it is built on the latest APIs optimized for security and performance.
From August 2018, new apps must target at least Android 8.0 (API level 26). From November 2018, app updates must target Android 8.0 (API level 26).
How do I get Delphi 10.2.3 to "target API level 26"?
Go to the AndroidManifest.template.xml file within your Delphi project directory and then change the "android:targetSdkVersion" from "%targetSdkVersion%" to "26". This was a bug in Delphi 10.2.3. It's now fixed in Delphi 10.3.2 and later.
Also make sure that you have Android API 26 selected within the Delphi SDK Manager Properties.
See also Deadline Approaching: Google’s new Android API level 26 Requirements.
See https://community.embarcadero.com/blogs/entry/deadline-approaching-google-s-new-android-api-level-26-requirements.