Batman Arkham Trilogy on Epic Games Store does not have any Arkham Knight DLC
From GameWatcher: "In a resounding generous move as part of Batman Day on Saturday, Warner Bros has let the entire Rocksteady Batman Arkham Trilogy be available for free to own on Epic Games Store, along with the LEGO Batman trilogy. This includes the Game of the Year editions of Batman Arkham Asylum and Batman Arkham City, and Batman Arkham Knight."
