None of special pages usually created by FlaggedRevs extensions are working on any of wikis on Miraheze (demonstrating here on Spanish public test wiki):
https://es.publictestwiki.com/wiki/Special:AdvancedReviewLog
https://es.publictestwiki.com/wiki/Special:ValidationStatistics
https://es.publictestwiki.com/wiki/Special:StablePages
https://es.publictestwiki.com/wiki/Special:PendingChanges
https://es.publictestwiki.com/wiki/Special:ProblemChanges
https://es.publictestwiki.com/wiki/Special:UnreviewedPages
"Edit review" section also is not displayed, however, they are present in search autocomplete. Multiple users are reporting same problems here:
https://www.mediawiki.org/wiki/Extension_talk:FlaggedRevs
Also reported in Wikimedia Phabricator:
https://phabricator.wikimedia.org/T151870