This is a quick guide on the ways of promoting your window 2016 on a read-only domain controller on an established domain.
Foremost build a Windows 2019 add an IP and be sure of its connection to the rest of servers and domains. Check all health tests like dcdiag, replmon etc.
From server manager click manage and select add roles and features
Check the box “active directory domain services”
Then select add features to have all necessary tools
Check the box “group policy management”
Select install / download
Allow installation/ download
When installation is done click the option “promote this server to a domain controller”
Select “add a domain controller to an existing domain”
Check all three boxes including read-only domain controller. Enter a DRSM password
Accept the default allowed password replication group
Allow the download to complete
In ADUC the domain controller will appear
To respond to correct IP configure DNS
This error will occur if this is your first directory 2019 deployment and you are using FRS. It can be resolved