Use adb sideload or install the .zip files directly from an SD card. Note: Most custom ROMs do not include Google Play Services, so you must flash "GApps" separately. Reboot: The first boot can take several minutes. Performance Considerations
Android 9 is the absolute limit for this hardware.
The custom ROM scene for the GT-i9200 in 2021 represents the best of Android: keeping hardware out of landfills. While development has likely stopped permanently now (as 2021 wraps up), the existing builds are frozen in time, working reliably for the foreseeable future.