I'm not aware of any official desktop application for Linux to sync Google Photos, but it is always accessible from the web at https://photos.google.com
If you're looking for a way to sync the files themselves between Google Photos and your computer, try a Google Drive client like Insync (paid, has free trial) or google-drive-ocamlfuse (free, open source).
Be sure to enable something in Google Drive so you can see Google Photos:
Organize photos & videos using Google Drive
You can move photos and videos into a folder, but the folders won’t become albums in Google Photos.
- On your computer, open drive.google.com.
- Click Settings > Settings.
- Check Create a Google Photos folder.
- Click Done.