Migrating Windows Server 2008 DCs to 2016/2019...

Q: How do I upgrade an Active Directory domain to Windows Server 2016/2019?

 

A: The recommended way to upgrade a domain is to promote domain controllers that run newer versions of Windows Server & demote the older DCs as needed. Details here:

 

https://docs.microsoft.com/en-us/windows-server/identity/ad-ds/deploy/upgrade-domain-controllers