**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
[x] Not searching 102 for +enwikibooks: Cookbook namespace
[x] Not searching 110 for +enwikibooks: WikiJunior namespace
[x] Not searching [102, 110] for +fawikibooks (کتاب_آشپزی cookbook) and ویکی_کودک wikijunior)
[x] Not searching 100 for +hewikisource
[x] Not searching 106 for +hewikisource
[x] 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 a minimum between informing, consensus, and responding)