How does a user enable another language than the default, base one?

Question

I went to settings and attempted to change the language in which my user will view the GUI. However, as the image depicts, there was no other choices than the base language, set by default.

If that'd be an on-prem environment, I'd try installing a language pack (and, potentially, take some additionally required steps). However, I work mainly with on-prem organizations and lack server access.

1. How do I display a non-base language in on-line environment?
2. How do I display a non-base language in on-prem environment?

Answer 1

On-Premise

1. Install the language pack on server
2. After installing, navigate to Settings -> Administration -> Languages to enable the newly installed language (might take a while)
3. New language will be available in Options for users

Online

Same as above, skip #1