In the mobile view of a Wikipedia page the "navigation box(es)" (also known as NavBox) at the bottom of articles are not shown. I don't mean 'collapsed by default', I mean that they are literally not there at all.
This is a piece of the content of an article that is being hidden from users. [equally, article categories aren't shown, but that's a different story]. Considering that the mobile team is develping the "Related articles" feature to automatically highlight relevant further reading, it seems counterproductive to deliberately hide the manually curated collections of related content that go with many articles.
Example:
The bottom of the mobile article "The Old Vic" https://en.m.wikipedia.org/wiki/The_Old_Vic goes from the 'external links' section straight to the 'talk' and 'other languages' mobile links.
Whereas the desktop version of the same article https://en.wikipedia.org/wiki/The_Old_Vic has a "Theatres in London" navigation box (shown in a 'collapsed' state by default). https://en.wikipedia.org/wiki/Template:Theatres_in_London