Yes, LEGO Fortnite Has Crossplay

To answer the question simply, yes, LEGO Fortnite does have crossplay. In a post created by LEGO, they explained that crossplay is on by default. What this actually means is that players on any platform can play the game together. So a Nintendo Switch LEGO Fortnite player can play with someone who is using a PC.

However, LEGO Fortnite is a bit different from normal Fortnite. Players have to opt-in to play together. That means that players have to invite each other to play in the same world at the same time. That is so random players cannot enter another person's world and destroy everything that they have created.

Does LEGO Fortnite Have Cross-Progression?

Much like crossplay, LEGO Fortnite does have cross-progression as well. So long as players are using the same Epic Games account when playing LEGO Fortnite, everything should save correctly. Players will just have to log in to their accounts and the world will start up like normal and work correctly.

Thanks to crossplay and cross-progression, there really is no limit on who can access a single world in LEGO Fortnite. So long as the host gives permission to other players to interact with their world, anyone can access a singular LEGO Fortnite instance. This gives everyone the ability to show off what they have created to their friends.