Hello Claudio,
I am sorry for not testing the script, because my test tenant is a pure Office 365 one.
The domain controller is the server which hosts your tenant. You can find it via following command:
get-mailbox <a mailbox on your tenant> | fl OriginatingServer
There will be a server FQDN in the result, such as CO1PR06A001DC02.NAMPR06A001.prod.outlook.com. You can use the server name as the parameter of Domain Controller. Here is the example:
.\Move-ExchangeDelegatedAuthToOrgID.ps1 -TenantVerifiedDomain sample.onmicrosoft.com -DomainController CO1PR06A001DC02.NAMPR06A001.prod.outlook.com
Please run the script. If it successes, run HCW again and let me know the result.
Thank you.
George Wu