What if Wikipedia first asks which language the user wants to use?
I don't know if it possible to do the following:

1. If Wikipedia website opens from a QR code from a mobile device
then show a pop up message (or a menu) with a list of languages.

2. Save the language choice via cookies on the mobile phone.

3. Next time when the user loads another article from Wikipedia, the article in the correct language is selected. If there is no article in the language, show a page "No article in your language is found. See below the list of languages for the article."