Disable Amazon FTV updates to use FireStarter upto OS(5.5.0)

1. Connect to your Fire TV via ADB
2. Run the command:adb shell pm hide com.amazon.device.software.ota
3. Run the command: exit

To re-enable updates, simply follow this guide again but replace hide with unhide in step 2. Alternatively, performing a factory reset will also re-enable updates.

Source aftvnews.com