As announced in the M365 message center post MC293777 Microsoft Search will over the course of November to December of this year execute phase one to deprecate the support of classic query rule based promoted results / best bets, and replace it fully with Bookmarks and Q&A answers.
Message center announcement: In order to improve the Microsoft Search experience, promoted results will no longer be supported in Microsoft Search for Organization level scoped searches and will be replaced by the Bookmarks and Q&A features.
