Is Fortnite particularly moddable? I know next to nothing about it, but didn't think it had a comparable modding scene to Minecraft and Roblox.

They have a special build of the Unreal Engine for Fortnite maps called UEFN. They have a similar pay for user playtime kind of payout model. They're trying very hard to be the the omni-game engine of choice.

https://www.unrealengine.com/en-US/uses/uefn-unreal-editor-f...