If this function is activated on the Huawei smartphone, the channels are connected during audio playback, which means that the left and right speakers reproduce the same content.

Android 10 (EMUI 10.0)
Step 1:  Open the  settings
Step 2:  Tap on  Accessibility features
Step 3:  Tap on  Accessibility 
Step 4:  Activate or deactivate  Mono audio
  1. Open the settings
  2. Tap on Accessibility features
  3. Tap on Accessibility 
  4. Activate or deactivate Mono audio

Huawei Instructions