Let’s look into /Tools/Options of LibreOffice 188.8.131.52 and then into language settings:
The language of user interface is English (USA).
The language of locale setting is German (DE).
In writing aids / available language modules i click on “edit” to see available languages: English (Canada, USA), Finnish, Indonesian, Irish …but no German!
Let’s look into /Tools/Extention manager:
German (DE-frami) spelling, hyphenation, thesaurus 2015.12.28 is installed.
So why is it not activated in the current version of Libre Office?