AFAIK there is no KDE/Plasma for Guix and correct link for nonguix/guix-nonfree is https://gitlab.com/nonguix/nonguix
Also, I think you can use the non-libre linux kernel build from substitutes instead building one yourself.
Also, I think you can use the non-libre linux kernel build from substitutes instead building one yourself.
Any particular reason why plasma is not upstreamed if not for lack of interest/contribution?