Our company interested in the Veeam for GCP to backup our IaaS, where we have the Microsoft Windows server 2019 with ADDS role onboard.
But still we have a concern - i did not found anywhere any settings in Veeam Backup for Google Cloud appliance to make sure that VB use the VSS based application-aware backup
Google snapshots do have this functionality, the difference is only in one key in the command
Unfortunately we don't yet support VSS in Veeam Backup for Google Cloud, as Google only currently support VSS per-disk. This means that a server with several disks (e.g. OS, Data, Logs) cannot be brought to a common VSS quiesced state - which is what we generally require for backup.
It is possible that your domain controllers only use a single disk, so it could work in your case, however we have not implemented it.
We continue to work with Google on methods to achieve VSS across all disks in a server, we are researching some alternative methods, and Google Cloud development is moving pretty fast (in your console code I see you are using beta functionality - however we cannot really implement beta api calls in Veeam Backup for Google)
So, right now your best option would be to use the Veeam Agent for Windows installed inside your DCs. This will give you a VSS-aware backup (and all the functionality of Veeam Explorer for AD). You can manage the agents from a Veeam Backup & Replication installation deployed on-premises or in the cloud.