Pressing and holding the virtual home button on the Xiaomi smartphone will launch the Google Assistant app by default, but you can disable this feature if you wish.

Android 10 (MIUI 12.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Additional settings
Step 3:  Tap on  Button shortcuts
Step 4:  Tap on  Launch Google Assistant
Step 5:  Choose  None
  1. Open the Settings
  2. Tap on Additional settings
  3. Tap on Button shortcuts
  4. Tap on Launch Google Assistant
  5. Choose None

Xiaomi Instructions