portage tries libkscreen2-1.72, but the directory name is actually libkscreen-1.72. I think this is the initial way it was done, but the KDE guys decided to change it and now seem to have changed it back. To see what's wrong, just try to compile the latest release of libkscreen2 Reproducible: Always
I guess we should move this back to be a new slot of regular libkscreen then.
in the meantime, maybe you could fix the source directory? :)
Thanks, it's moved back to regular x11-libs/libkscreen now.