Since Norsk bokmål Wikipedia is located at no.wikipedia.org, not nb.wikipedia.org, for historical reasons, the system language code "nb" must probably be mapped manually to the corresponding wiki.
- Set Android system language to "Norsk bokmål" (language code "nb_NO").
- Open the Wikipedia app (and go to Today / Mainpage).
The interface language is Norsk bokmål, and the page is from Norsk bokmål Wikipedia (no.wikipedia.org)
The interface language is Norsk bokmål, but the page is from English Wikipedia (en.wikipedia.org)