DISCLAIMER: This process will overwrite the current Android ROM on your TV box. I have tested these steps on my own devices, but I am not responsible if you damage or brick your device. Verify the ROM will work on your device before starting and make sure to backup any data you do not want to lose before proceeding.
- Download DaivietPDA's Android TV 9 ROM Download | Alternate Download
- Download Amlogic Burning Tool v2.2.0 Download
- Extract Amlogic Burning Tool v2.2.0
- Install Amlogic Burning Tool v2.2.0
- Launch Amlogic Burning Tool v2.2.0
- Go to File > Import Image > Browse to and select DaivietPDA's Android TV ROM .img file
- Click the Start button in the top right corner of the application
- Connect the S912 TV box to the PC via USB cable
- Press the reset button (sometimes hidden inside the AV port)
- Wait for the ROM to copy over to the device
- Once the process completes (100%: Burning Successfully) click the Stop button
- Disconnect the TV box from the PC USB
- Connect the TV box to an HDMI display and power it on
- Enjoy a clean and fast Android TV experience on your S912 device
Source: https://daivietpda.com/2020/07/rom-atv9-android-9-0-cho-amlogic-s912/