Assume that you install a non-English version of SQL Server 2016 by using the graphical user interface. You also use the Product Update feature to perform a slipstreamed install with RTM + GDR update. In this situation, when you run Setup again, for example, to add features, the display language of the landing page changes to English.
The issue was first fixed in the following cumulative update of SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. We recommend that you download and install the latest cumulative updates for SQL Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology that Microsoft uses to describe software updates.