Your users see an error message during the Google OAuth process describing that Google hasn't verified this app. This guide describes how your user's Google Workspace admin can add your application to their allowlist (also called 'Whitelisting').
1. The developer of the application needs to provide the Client ID of your google project https://console.developers.google.com/apis/credentials to the Google Workspace admin.
2. The Google Workspace admin of the organisation then needs to:
b. Add the full client_id provided by the developer of the application.
Example format of a client_id