gphotos-sync is a command line tool for backing up Google Photos (including separate albums) using the Google Photos Library API, for Linux, macOS and Windows. Use it periodically to grab all newly added photos, keeping a complete Google Photos backup on a server or desktop.
This tool is specially useful after Google's announcement that Google Photos will stop syncing to Drive starting July 10, 2019, which means that some tools for backing up Google Photos to your computer will stop working (affecting Insync for instance, a commercial Google Drive client that runs on Linux, macOS and Windows).