I also have access to the Sharepoint Desktop client
Is this the OneDrive Sync client?
Is it possible to create a Sharepoint that has APIs to synchronise the data with data stored on Google Cloud Platform?
SharePoint has APIs for just about anything you want to do with content!
So, assuming by sync, you want the same files to be available in both systems... Or more likely, a one-way sync from a "master" library to a "clone" library...
- Use the OneDrive sync client to sync a library's content to a local PC or server, and then, assuming that it exists, use the Google sync client to sync to the same location on that PC.
- Write your own sync client (C#/Visual Studio or just about any other toolset) that monitors the date of last change in one system and copies the files to the other. SharePoint has REST APIs that can do the queries and the file copies. I would assume Google has something similar.
- Use one of the third party solutions... do a web search for "sync sharepoint library with google drive"
SharePoint REST API: https://docs.microsoft.com/en-us/sharepoint/dev/sp-add-ins/get-to-know-the-sharepoint-rest-service