In https://gitlab.wikimedia.org/toolforge-repos/luthor/-/blob/master/config/locales/en.yml?ref_type=heads#L64 I currently see one entry for Chinese, which is what I get to translate on translatewiki.net as a translator.

But when I visit https://luthor.toolforge.org I see that in the dropdown to the right, just below the logo, there are Zh Hans and Zh Hant options, which at the moment I cannot translate.

At the bottom of the same page, when I click the respective button, I see "Mandarin Chinese (中文)" which is a yet another entry. Though looking closely on that list, I see that the language names it contains are not currently translatable at all, as I see, for example Latin, and it is not included in the localisation file.