You can install user interface language pack (MUI pack, UI pack) into any default language mutation of Windows 10 of any build. You can even install English (en-us) language pack into a non-English Windows 10.
First you naturally need to download the language pack. In my MVP/MCT case, I downloaded it from MSDN subscriber downloads portal. It comes in the form of ISO file containing all the available language packs in the form of individual CAB files both for x64 and x86 builds.
ISO can be opened within Windows Explorer so no problem mounting it from GUI and accessing its contents from command line later.
Then, you run the following command against your desired MUI CAB pack to be installed:
dism /online /add-package:"E:\x64\langpacks\Microsoft-Windows-Client-Language-Pack_x64_en-us.cab"
After DISM finishes you must restart the operation system and only then you should be able to open the Languages control panel and select the newly installed UI language as the primary choice.