Since v8.05, Syncovery natively supports Google Cloud Storage. You can choose it in the protocol selection on the Internet dialog.
Since v10.11.0, Syncovery uses Google Cloud Service Accounts to connect with Cloud Storage. Please see Synchronizing Files with Google Cloud Storage using Syncovery for details.
As an alternative, you can use the Amazon S3 compatible API for Google Cloud Storage. In that case, choose S3 as protocol, and choose Google Cloud Storage as provider, or specify your bucket like this: bucketname@storage.googleapis.com
You can get your Access ID and Secret Key via the Interoperability tab sheet of the Cloud Storage Settings page
https://console.cloud.google.com/storage/settings
Please don’t choose unsupported features like Reduced Redundancy, as they will cause errors.