OK, the lack of the Epic Games Launcher was proving problematic...all the tutorials tell you to get project files from the marketplace and you seemingly can't download files without the launcher. None of the Unreal+Linux docs even mention the launcher. Turns out there's a thing called Lutris, it's in the Fedora repos, that installs the launcher with Wine. Yet again, it somehow Just Works™. Things aren't going fast, but they're going well enough, I reckon, given my stubborn insistence on Linux.