Note: I have experienced an accidentally reboot. Use at your own risk.
You need to open the official flash tool and load the image package “S813_JingPad_C1_1.0.0002.011_user_202111011157.pac” first.
Then click the second button (Settings), here you can find where the “Trustos” file and “Teecfg” file are located; Copy them to somewhere else.
Now load the unofficial image package, go to Settings, and replace “Trustos” and “Teecfg” with the file you just copied:
Then flash it to your JingPad. You should be able to use fingerprint and face authentication now: