https://www.gamespot.com/articles/fortnite-week-2-secret-battle-banner-location-seas/1100-6462272/

Season 6 of Fortnite rolls on. Another set of weekly challenges are now available to complete, and as usual, if you manage to finish all of the ones from a given week, you'll in turn complete a Hunting Party challenge--this season's equivalent of the Road Trip challenges from Season 5.

The reward for completing a Hunting Party challenge is a special loading screen, which hides a very subtle hint to the location of a free item hidden around the island. Typically, the item in question is a free Battle Star, which levels your Battle Pass up by one tier once collected, but toward the end of Season 5, Epic began hiding banners in their place.