When building for Android, Titanium should target API Level 28 (aka: Android 9.0) by default if installed under the Android SDK.
Titanium currently targets up to API Level 27 (aka: Android 8.1).
Titanium currently does not target API Level 28 by default. This is a safety precaution until Titanium addresses all Android P breaking changes. But a developer can opt-in to targeting the newest API Level (at their own risk) by adding the following to their "tiapp.xml" file.