I'm currently finishing my Task Sequence for 20H2 installing "Language Packs" inside TS and it is working fine with this manual:
https://techcommunity.microsoft.com/t5/core-infrastructure-and-security/windows-10-multilanguage-deployment-with-memcm/ba-p/1347144#h_38613590318151588256071004
- Install Language Pack
- Install Local Experience Pack (Appx)
- Register Local Experience Pack with local admin user
- Set Language with Script + XML
Just hanging on adding FODs like Handwriting, TextToSpeech at this moment for having the full Language Features installed.
Will update you on this.