Arch Linux uses its own build system, and my package is pretty much identical except for using the latest git HEAD instead of a tagged tarball and actually listing the relevant optional dependencies.
So unless it is some sort of DE issue (which has happened before, cf. mysterious instant segfaults under KDE) then it would almost have to be an issue with the actual plugin file roger64 attempted to add.

If he doesn't reply first, I might go ahead and install KDE to test it...