Many projects have noticeboards that allow searching through the archives. These have worked in the past by appending "prefix:<whatever noticeboard>" to the search term requested.

This no longer works in enwiki or commons, it returns zero results but gives the following error:

A warning has occured while searching: The namespace found in the search term prefix: is not compatible with the namespaces requested. You can fix it by prefixing your query with all:.

This occurs both logged in with Monobook and logged out with whatever the default is these days, on both Chrome and Firefox.

Sample searches that should return results:
https://en.wikipedia.org/wiki/Special:Search?search=test&prefix=Wikipedia%3AAdministrators%27+noticeboard&fulltext=Search&fulltext=Search&searchToken=am1sglpn31h2rzpnl0sqwb107
https://commons.wikimedia.org/wiki/Special:Search?search=test&prefix=Commons%3AUndeletion+requests&fulltext=Search+archives&fulltext=Search&searchToken=d6nmyf8sl60mta4i5ouz5hroi