Alright, this may not be perfect but I'll try my best to write down everything I know about the Fortnite lore, cause theres a lot and I will absolutely miss and mess up most of it, but I'll try my best anyways. Take some of the lore with a grain of salt, thank you!

Welcome to the loop, if you die you forget everything, but if you win you remember what happened, hence why you are a "looper", people with a special kind of mask can bypass the "loop" properties.
In Chapter 1 season 1-3, there is no lore
In Chapter 1 season 4, a meteor struck, introducing one of "The Seven" members, "The Scientist"
In Chapter 1 season 5, a cube appeared out of nowhere and every hour, it rotated, eventually getting itself into Loot Lake
In Chapter 1 season 6, the cube manifested itself into an island (lifted the house) and more came around
In Chapter 1 season 7, the ice king appeared and covered the map in snow
In Chapter 1 season 8, I forgot
In Chapter 1 season 9, Neo City appeared and a big battle with the mech and the monster happened, with "Sigularity" piloting the mech
In Chapter 1 season X (10), Everything was going bad because the mech unstabilized the Zero Point and the Zero Point controls all realities
In Chapter 2 season 1, after the black hole event, a new island appeared
In Chapter 2 season 2, there was a island-wide battle between Ghost and Shadow, then midas released "The Device" and pushed storm, accidently flooding the island
In Chapter 2 season 3, the island was flooded, and the island was filled with places that were made of scrap
In Chapter 2 season 4, the avengers has invaded the island, protecting it from galactus
In Chapter 2 season 5, Galactus unstabilized the zero point, causing more craziness
In Chapter 2 season 6, The Foundation starts fixing the zero point
In Chapter 2 season 7, aliens invaded the island
In Chapter 2 season 8, a mother ship fell on the island and now there is cubes everywhere, and the cube queen starts taking over the island, but The Seven along with the loopers (players) flipped the island
In Chapter 3 season 1, brought a slew brand new map with a introduction to the new island
In Chapter 3 season 2, The Seven and IO went to war
In Chapter 3 season 3, after the collider got destroyed, the Zero Point got unstable but everything was chill
In Chapter 3 season 4, The herald brought chrome that spreads and she wants to blow up the island
In Chapter 4 season 1, After the most boring live event (it was about the island blowing up and us doing minigames to restore reality), we got a new map
In Chapter 4 season 2, the rift gate blew up bringing Mega City, based off of Tokyo Japan
In Chapter 4 season 3, the center of the island collapsed revealing ancient temples and a whole jungle
In Chapter 4 season 4, vaults I guess?
In Chapter OG season OG, we go back through Chapter 1
In Chapter 5 season 1, we got a new map, and peely is missing
In Chapter 5 season 2, literal (Greek) gods invade the map after pandoras box opened
In Chapter 5 season 3, the wasteland appears after pandoras box got unstable
In Chapter 5 season 4, the avengers come back to save the island from doom himself
In Chapter Remix season Remix, Rappers take over the map