Pandoc: setting language of exported Word docx

I have just checked again, and with Pandoc v 2.9.2.1 it seems to set the language correctly:

Hooray!! Thanks, Pandoc community! <3

Would be interesting though to know when exactly it was added (couldn't find a mention in the https://pandoc.org/changelog.txt).

There is currently no way to set the language of a doc, docx, or odt document output by pandoc. A pandoc GitHub issue discusses this problem (noted in the comments by @Serge Correia).

Indeed, localization in other formats goes through templates, but the doc, docx, and odt equivalent of a template, reference files, only set a few selected styles and properties. For instance, reference-docx: (from the pandoc README)

The contents of the reference docx are ignored, but its stylesheets and document properties (including margins, page size, header, and footer) are used in the new docx.