This system will display the winners of previous rounds on the Player Reference devices. It works for your duo map even if new teams are chosen each round. To use this system, you need a Tracker device, Player Reference devices, and the End Game device. This system works for any type of map with duos and multiple rounds—you can use it for box fights and zone wars.
https://dev.epicgames.com/community/learning/tutorials/19w44/fortnite-uefn-duo-win-system