Google Play will require new/update App to target API level 28+ in 2019

Google Play Console will continue to require that apps target a recent API level:

• August 2019: New apps are required to target API level 28 (Android 9) or higher.
• November 2019: Updates to existing apps are required to target API level 28 or higher.

Existing apps that are not receiving updates are unaffected and can continue to be downloaded from the Play Store.

source: Android Developer Blog - Expanding target API level requirements in 2019