If I search for Help: or Template: on either meta.wikimedia.org or mediawiki.org, I get an in-page error in red:
An error has occurred while searching: The search backend returned an error:
(with no text).
E.g. search for Help: or Template: , or on meta search for Research: . But searching for Special: doesn't give an error.
This doesn't happen searching on enwiki. I don't know for sure if meta and mediawiki use lucene
Version: unspecified
Severity: normal