Install Drive for Desktop on Mac
Here is the Simple Guide to Install Google Photos on Old MacBook Air, MacBook Pro, and Latest Apple M1 Chip.
Method 1. Use Settings to Backup Photo Library
Here is the Simple Drive for Desktop Setting to Backup System Photo Library and iCloud Photos to Google Photos.
Method 2. Add Photos Library Folder for Backup
Here is the Guide Add System Photos Library Folder as a Backup Folder to Upload all Photos and Videos to Google Photos Cloud.