Rule 103.2.a.2
Must be a champion unit with a champion tag that matches the tag on your Champion Legend. Example: Loose Cannon has the tag Jinx. Therefore, a player could choose Jinx, Rebel or Jinx, Demolitionist as their Chosen Champion, because they also have the tag Jinx. Example: Tibbers has the tag Annie, but it is a signature unit, not a champion unit. It cannot be your Chosen Champion, even if your Champion Legend has the tag Annie.