Epic CEO Tim Sweeney recently stated that Epic has no plans to update Fortnite for handhelds because anti-cheating on Steam handhelds is difficult to implement.
Steam Deck is an open platform handheld that you can do anything with, even as a small Linux computer. So it can install third-party software and operating systems, and even be able to enter competitor stores, such as epic stores. While Fortnite isn't a Steam platform game, it should still be able to run on Steam Deck.
Sweeney says they put a lot of effort into making Epic's "Easy Anti-Cheat" compatible with Steam Deck, which is a reliable anti-cheat system for other games on Steam Deck but not for Fortnite.
And Sweeney's follow-up tweet explained: "Fortnite's scale makes it more vulnerable to attack than other games. The anti-cheat model is different in each game, which is related to the number of active players and the profits obtained by selling cheats (plug-ins), etc. Therefore, it is not enough for one game to be able to climb on another game platform that may have 10x, 100x or 1000x players."
For now, it seems that Epic's attempt to protect a popular game like Fortnite from cheaters on multiple custom Linux distributions consumes too many resources, and the rewards that may be received on Steam Deck are not so great at the moment.