Some apps require access to make changes to system settings, but this is not security related access to the lock screen or passwords, but to change the ring tone or background, for example.

On the Oppo smartphones with ColorOS, these settings are somewhat hidden deep within the app permissions.

Android 10 (ColorOS 7.0)
Step 1:  Open the  Settings
Step 2:  Tap on  App management
Step 3:  Tap on  App permissions
Step 4:  Tap on  Set subordinate permissions
Step 5:  Tap on  Rarely used permissions
Step 6:  Tap on  Modify system settings
Step 7:  Tap on  App  you want
Step 8:  Enable or Disable  Allow modifying system settings
  1. Open the Settings
  2. Tap on App management
  3. Tap on App permissions
  4. Tap on Set subordinate permissions
  5. Tap on Rarely used permissions
  6. Tap on Modify system settings
  7. Tap on App you want
  8. Enable or Disable Allow modifying system settings

Oppo Instructions
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