The following Gerrit repositories are owned by groups that are not "Visible to all users" and thus appear as a 404 error:
mediawiki/extensions/DataTable2 mediawiki/extensions/ShowRealUsernames mediawiki/extensions/TemplateStyles mediawiki/extensions/TranslationNotifications
The following repositories are owned directly by a user rather than a group at all
mediawiki/extensions/Monstranto mediawiki/extensions/QuickInstantCommons mediawiki/extensions/PageSchemas
The following repositories have a LDAP group configured as the owner, which probably isn't a problem, but confused my script, so I'm listing them here for completeness
mediawiki/extensions/Cognate mediawiki/extensions/FileExporter mediawiki/extensions/FileImporter mediawiki/extensions/InterwikiSorting