As RelatedSites extension has been undeployed from Wikimedia projects today[1], a question arises: who will maintain it in the future? Unless someone volunteers to maintain it, we will probably eventually have to archive the repository. According to WikiApiary[2], besides WMF it's used only on vojnaenciklopedija.com (ping Zoranzoki21).

---- [1] https://phabricator.wikimedia.org/T128326 [2] https://wikiapiary.com/wiki/Extension:RelatedSites