Installed GYB without issue (macOS 15.6) and followed the instructions to create Client ID and secret. Upon reaching the step to authorize with Google, I was presented with the following error message...
Access blocked: GYB has not completed the Google verification process
GYB has not completed the Google verification process. The app is currently being tested, and can only be accessed by developer-approved testers. If you think you should have access, contact the developer.
If you are a developer of GYB, see error details.
Error 403: access_denied
I'm using GYB with a personal Gmail account, not a Google Workspace account.