TYPO3 Core

In TYPO3 version 11 CKeditor version 4 uses language_list so editors can give a paragraph or line in a foreign language the correct output: https://ckeditor.com/docs/ckeditor4/latest/api/CKEDITOR_config.html#cfg-language_list

Example:
config.language_list: ['de:German', 'fr:French', 'en:English', 'uk:Ukrain']

This function seems to have been migrated to: https://ckeditor.com/docs/ckeditor5/latest/features/language.html. The configuration is different from the latter and doesn't seem to work.

Example:
config.language.textPartLanguage:
- { title: 'German', languageCode: 'de'}
- { title: 'French', languageCode: 'fr'}
- { title: 'English', languageCode: 'en'}
- { title: 'Ukrain', languageCode: 'uk'}

According to CK Editor developer the above configuration should work. They claim the TextPartLanguage plugin is missing.