Background
It seems there are several disjunctions between wgContentNamespaces and wgNamespacesToBeSearchedDefault. The latter is what is reflected as "Content" in the Special:Search page.
This was noticed because "Risotto" doesn't return any results on en.wikibooks, even though there is the page Cookbook:Risotto. I have created a diff list between the two variables using P5740
- Not searching 102 for +aswikisource
- Not searching [100] for +bnwikisource
- Not searching 102 for +enwikibooks: Cookbook namespace
- Not searching 110 for +enwikibooks: WikiJunior namespace
- Not searching [102, 110] for +fawikibooks (کتاب_آشپزی cookbook) and ویکی_کودک wikijunior)
- Not searching 100 for +hewikisource
- Not searching 106 for +hewikisource
- Not searching 110 for +hewikisource
- Not searching [102] for +hrwiki
- Not searching [104] for +ltwikipedia: vikiprojektas (wikiprojects ? why is that in contentnamespaces ?)
- Not searching [102] for +srwikibooks: кувар (cookbook)
- Not searching [100] for +srwikisource
- Not searching [100, 110] for +trwikibooks: yemek (cookbook) and vikiçocuk (wikijunior)
Some of these might be desirable, but likely most not.
Success criteria
Reach out to the communities affected and ask if they would like the setting to be changed. Create subtasks to track the technical configuration changes requested (if any)
Timeline
This was unplanned work. The actual change should be technically trivial, reaching out and discussing with communities will take a little longer (weeks at minimum between informing, consensus, and responding)