This is the biggest mess I have ever seen. Microsoft. Are you kidding us? Are you still considering and developing for enterprises or only for end users?
We are an English global company with more then 90 offices worldwide which is using 99 percent English only Windows 10 image to simplify support but of course we need localized keyboard layout and language features like basic typing (e.g. for Japanese users with IME support) handwriting recognition (for tablets), text-to-speech, speech or ocr which are not in the normal LP.iso but in the FOD Disc1.iso as they are "Microsoft Windows Language Features" but if you select e.g. the Japanese LPX from the store it also includes these components.
When I look into the "LocalExperiencePack" folder of the SW_DVD9_NTRL_Win_10_1809_32_64_ARM64_MultiLang_LangPackAll_LIP_X21-91305.iso I cannot see the LPX for Japanese and many other limportant languages like German etc. but they is available in the MS Store as LPX files!!!! Why are you doing this? Why is the "LocalExperiencePack" subfolder of the LP.iso incomplete? How should an enterprise automate this configuration for a Japanese user? Especially as our users do not have Admin rights on their machines because of Security reasons and cannot go to the store and add these components by themself.
Why does a simply language addition via the Settings app or MS store requires admin rights and the UAC pops in? Especially as such a Langage addition is a not a machine but a user only (profile setting).
Again - a complete mess! You are developing for end users only and change things which are useless for enterprise or even worse create unsolvable trouble for them.
I can not see any stringent strategy in the topic at Microsoft. Especially as MS discontinued the option to offer LP and FOD is WSUS since Windows 10, version 1709. Now you can only download directly from Microsoft store servers.
But to ensure that Windows 10 clients with version 1709 or later also automatically download these optional components if the user installs an additional language when a WSUS server is configured, this WSUS bypass must be explicitly allowed via a corresponding GPO setting:
1. Go to Computer Configuration => Policies => Administrative Templates and then System.
2. Double click or open “Specify settings for optional component installation and component repair”
3. Make sure “Never attempt to download payload from Windows Update” is NOT checked
4. Make sure “Download repair content and optional features directly from Windows Update instead of Windows Server Update Services (WSUS)” is checked.
Source: https://www.stephenwagner.com/2018/10/08/enable-windows-update-features-on-demand-and-turn-windows-features-on-or-off-in-wsus-environments/
Besides you need to consider, that the auto-download of FOD components only works if your user has admin rights - otherwise you see the LP sub components like "Basic typing", "Handwriting" or "Speech" in the Language Options window of the Settings apps but they are not downloaded - even if you click the "Download" buttons you don't get any error message or feedback - very poor UI design Microsoft!
Again very annoying the whole topic - especially as they is more or less no consistent documentation or communication except this insufficient blog here....