However, the actual customer's AADC server infrastructure is very diverse, so there are many concerns in making an upgrade plan. So, I would like to share a possible upgrade plan considering the customer's AADC server infrastructure.
Things to consider in advance
First of all, if the Windows Server version of the AADC server is 2012R2 or earlier, OS reinstallation is required. In-Place Upgrade for Windows Server with AADC is not supported.
I also tried OS In-Place Upgrade once, the sync of AADC was normal, but I couldn't change the configuration at all.
It is also important to consider SQL Server. When using LocalDB, it is automatically upgraded to SQL 2019 Local DB within the upgrade process. However, if a separate SQL Server 2012 or earlier is used, reinstallation or upgrade to SQL Server 2014 or higher is required. Actually, a higher version would be better.