In addition to the default ringtone on the Xiaomi smartphone, each contact can also be assigned their own ringtone, so that we can recognize who is calling by hearing the sound alone. We can choose from the pre-installed and custom ringtones.

Android 10 (MIUI 12.0)
Step 1:  Open the  Contacts app
Step 2:  Choose a  contact
Step 3:  Tap on  (Default) ringtone
Step 4:  Choose a  ringtone
  1. Open the Contacts app
  2. Choose a contact
  3. Tap on (Default) ringtone
  4. Choose a ringtone

Xiaomi Instructions