Problem:
When running :
ionic cordova run android -l (or other options)
the error ERR_CLEARTEXT_NOT_PERMITTED appears from android emulator or device when it attempts to load your application.
Solution:
Open file: <Ionic app home>\platforms\android\app\src\main\AndroidManifest.xml an add below attribute to the element <application/>
android:usesCleartextTraffic="true"
Save and re-run the command in problem section, your application should launch!