I can duplicate your error.
No matter which theme you try to install, this happens:
kpackagetool5 -t Plasma/LookAndFeel -i /tmp/com.github.vinceliuice.Layan.tar.xz
Error: Installation of /tmp/com.github.vinceliuice.Layan.tar.xz failed: Could not install dependency: 'kns://colorschemes.knsrc/api.kde-look.org/1325239'
It fails to install the dependencies.