Package: xdg-utils Version: 1.1.3-4.1xdg-mime query filetype simply exits when the detected desktop is KDE, and KDE_SESSION_VERSION is set to anything other than 4 or 5.
This is a slight problem when it is set to 6, as is the case with plasma 6 from experimental.
Of course, given that plasma 6 is still in experimental, not sid, that means that this isn't a complete surprise, but it definitely breaks things like wl-copy.