From OTRS: https://ticket.wikimedia.org/otrs/index.pl?Action=AgentTicketZoom;TicketID=11286891

I have noticed a small bug with the android version of the Wikipedia app (unsure if any other version is affected). I have left a review on the Play store but thought I'd also email you in case this isn't seen.

As I mentioned it is just a small bug. If you open an article and click on a section that actually has nothing but a link to a separate page in the app you do not see the link.

To help you understand go to the following link, a Wikipedia page for the writer H.P. Lovecraft
https://en.m.wikipedia.org/wiki/H._P._Lovecraft
If you go to the bibliography subsection in a browser you will see a link to another separate page just for the bibliography. However if you go to the page via the app and go to to the bibliography subsection there is nothing as if it is not displaying the link and just the subsection title.

This appears to happen on any Wikipedia page where a subsection is just a link to a separate page.