Debug on Android devices
You enable debugging in different ways on different Android devices. Look for USB Debugging under Developer Options. Tap Build number in Settings > About several times to show Developer Options.
Select a debug build configuration to build the application for debugging.
Note: Qt Creator cannot debug applications on Android devices if Android Studio is running. If the following message appears in Application Output, close Android Studio and try again:
Ignoring second debugger -accepting and dropping.
See also How To: Develop for Android, Developing for Android, and Configure on-device developer options.