Hello,
When you add a new KMS host key to Active Directory, it creates a new activation object but does not replace the existing object. Each KMS host key corresponds to a unique activation object in AD. So if you add a new host key for Windows Server 2019, it will create a new activation key for that specific version and will not affect the existing activation object for Windows Server 2016.
The KMS client (the computer you want to activate) will automatically search for and use the activation object that matches its version. So, a Windows Server 2016 computer will continue to use the 2016 activation object, while a new Windows Server 2019 computer will use the new 2019 activation object.
Best Regards,
Yanhong Liu
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