I. Observed: the language code is 'sr' appears in the sidebar, because the article is available in it and linked in Wikidata.
Note that this bug is not about Serbocroatian ("Srpskohrvatski / српскохрватски") - this language does appear.
- Enable Compact Language Links
- Go to https://en.wikipedia.org/wiki/Novi_Sad
- Click "65 more" (or other count) in the "other languages" interlanguage interwiki list of the sidebar.
- Type "sr" or "Српски" in the search bar.
II. Expected: a link to Serbian ("Српски / srpski") appears.
III. Observed: only Srpskohrvatski appears.
This is on the verge of "Unbreak Now!" because thousands of users enabled this Beta Feature, and it's not showing a language.