In this case, it is important to know the exact model number of the device. Usually, it starts with the letter 'M'. For example MT002J/A.
The model (MT002J/A -> iPhone XR, Black, 64GB) was built for use in Japan. Unfortunately, the shutter sound can’t be disabled on this device.
Tip: To identify the model number, go to Settings > General > About. You'll see the part number to the right of Model. To see the model number, tap the part number.
All in all, Apple Support is a good way to get additional info on the issue you might be having with your particular iPhone XR.