Feature summary:
Major multilingual MediaWiki sites such as Wikidata, Wikimedia Commons, Meta, etc. do not seem to take into account the preferred language of the browser for users that are not logged in. The GUI is always in English. This is not user-friendly and discriminates against users whose native language is not English.

Use case(s):
When users are not logged in:

• for multi-language sites, e,g. Wikidata, Wikimedia Commons, Meta, or WMBE site, users would expect the GUI and the translated page in their native language instead of the English content;
• users would like to see Wikipedia content with the GUI in their own language, irrespective of the language of the content.

Benefits:

• Non-logged in users would see the GUI, and for multi-lingual sites also the content, in their native language, instead of default English.
• Logged in users would continue to select their preferred language via local or global preferences.