When activating a timer in the clock app on the Huawei smartphone, the ringtone icon is already visible. We can set a custom ringtone for the expired timer that will remain set for subsequent timers.

Android 10 | EMUI 10.0
Step 1:  Open the  Clock app
Step 2:  Tap on the  bell icon
Step 3:  Choose a  timer tone
  1. Open the Clock app
  2. Tap on the bell icon
  3. Choose a timer tone

Huawei Instructions