When I did sudo-qubes-dom0-update @kde-desktop-qubes, it gave me a list of the core packages it was attempting to install in the sys-firewall popup terminal. I copied and pasted the core list from there, used dnf to install:
sudo dnf install apper breeze-icon-theme colord-kde dolphin kcm_systemd kde-runtime kde-settings-pulseaudio kde-style-breeze kdelibs kdeplasma-addons kdialog khelpcenter khotkeys kinfocenter kmenuedit kmix konsole5 kscreen ksysguard kwin phonon-qt5-backend-gstreamer plasma-breeze plasma-desktop plasma-desktop-doc plasma-pa plasma-user-manager plasma-workspace polkit-kde qt5-qdbusviewer sddm sddm-breeze sddm-kcm sni-qt
Then switched per instructions here KDE | Qubes OS
Everything works except, missing icons on the dock (start icon, + vm nm icons). All other icons are there (including virtual desktops). Yay, finally runing KDE in 4.1.
One other issue: The window manager has locked up twice in the few hours since I swiched…not sure why yet. I restart it via a console: ctrl-alt-F2 to get a console, then log in, then sudo systemctl restart sddm
edit: vm color on window borders is nto working 