Posting here in case someone needs it.
How to disable long press of the home button (Or how to change to Alexa from Google assistant)
- Go to Settings > Apps & notifications > Advanced > Default Apps
- Select “Assist & voice input”
- Select “Assist app”.
- Change to “None”. If you have Amazon Alexa installed, then you can change to Alexa as well at this step.
Alternate steps: How to disable Google assistant completely
- On your Android phone or tablet, touch and hold the Home button or say “Ok Google.”
- Hit the Compass button (toward the right side).
- Tap the top-right avatar and then Settings > Assistant.
- Under “Assistant devices,” select your phone or tablet.
- Turn off Google Assistant.