Terms of Service
In order to authenticate the application with your Google Photos account, please follow the next steps:
Launch the app on your Apple TV
The application shows an unique authentication code. Take note of it.
Using any other device (your phone/tablet/computer) navigate to https://gphoto.app and enter the above code in the text field on the main page. Click "Activate".
Click on "Sign in with Google" which will redirect you to the Google's authentication mechanism.
Authenticate with your Google account.
The application is ready to use.