Apps that want to get deep functionality into the system on the Oppo-Smartphone have to be identified as device administrators (device managers). A classic example is the "Find my device" feature from Google, which is installed by default on an Android device. To remotely reset the Oppo-Smartphone to factory defaults, the app has to be a device administrator.

Device administrators can be managed under ColorOS in the security settings.

Note: Any app cannot be defined as a device manager. The app must request access itself. Only then will it be visible in the settings to activate it.

Android 10 | ColorOS 7.0
Step 1:  Open the  Settings
Step 2:  Tap on  Security
Step 3:  Tap on  Device admin apps
Step 4:  Enter  Security-Code  and confirm with  Activate
Step 5:  Tap on desired  App
Step 6:  Tap on  Activate/Deactivate
  1. Open the Settings
  2. Tap on Security
  3. Tap on Device admin apps
  4. Enter Security-Code and confirm with Activate
  5. Tap on desired App
  6. Tap on Activate/Deactivate

Oppo Instructions