After starting the camera app on the OnePlus smartphone, a timer or countdown for a self-timer can be set directly in the upper area, for example to capture a family photo in its entirety.
In addition to deactivating the function, we can choose between the following options:

Android 10 | OxygenOS 10.0
Camera timer -  Open the  Camera app
Camera timer -  Tap on  Timer
Camera timer -  Choose  3s / 5s / 10s  or  Off  to disable the timer
  1. Open the Camera app
  2. Tap on Timer
  3. Choose 3s / 5s / 10s or Off to disable the timer

OnePlus Instructions