To match Android, we should send in the legacy language variant code (like `zh-tw`) to the read more `langCode` parameter in the footer setup Javascript. This logic can be added [[ https://github.com/wikimedia/wikipedia-ios/blob/main/Wikipedia/Code/ArticleWebMessagingController.swift#L70 | here ]]. The legacy language variant can be found by referencing `articleURL.wmf_languageVariantCode` to get the modern language variant code, then checking it against `WikipediaLookup.allLanguageVariants` to grab the equivalent legacy language variant code.
While we're here, we should look into why "About this article" and "Read more" display as English as see if this change fixes it:
{F58350400}
Reference: [[ https://github.com/wikimedia/apps-android-wikipedia/pull/5167/files | Android PR ]], [[ https://phabricator.wikimedia.org/T378394 | Android task ]]