Although it’s possible to install and use the Epic Games Launcher on Linux using Lutris, at the moment, you can’t actually play Fortnite. This is because the game’s anti-cheating software detects that something is wrong and rather than trying to find out what, it decides to err on the side of caution, preventing you from accessing the game. If you’re interested in playing Fortnite on Linux, there really isn’t much you can do except let Epic Games know.