In case anyone else happens along this thread with a similar question: the following is the list of built-in languages (as of 12/25/2019)
- English (United States)
- Nederlands
- Français
- Deutsch
- Italiano
- 日本語
- Polski
- Português do Brasil
- Português
- Русский
- Español
- Türkçe
If you need to use one of the above languages, navigate to Dashboard > Settings > Site Language and choose your preferred language.
To use a language that is not listed above, you can download and install the language pack plugin according to the instructions on the WordPress Language Packs page.