https://www.pcgamer.com/fortnites-flying-loot-lake-island-is-moving-around/

The island floating above Loot Lake is moving, folks. After the mysterious cube kinda… melted into it last season, we’ve now got a floating island above Loot Lake. Players are now reporting all over social media that the island is floating, moving across the map from place to place—though where it’s actually going remains a mystery. If that sentence means nothing to you, maybe catch up on what’s new in Fortnite Season 6 before proceeding. 

Reports place it at or near the various runes left by the cube as it traveled the map during Season 5. Conflicting reports place the fugitive island near retail row and salty springs, or maybe in the opposite direction, near pleasant park. The common theory, however, seems to be that it’s heading towards the various runes left by Season 5’s mysterious cube—possibly to affect the corrupted areas it left near them.