I've figured a few things out I've not seen posted anywhere so I will conclude this thread with a way that works for me. I've seen posts all over with people that gave up on almost any distro with KDE plasma in a VMWare guest.
tl;dr - switch to Wayland. I am not well versed in the merits/deficits of using Wayland but in my case it allows everything to work correctly using KDE (Kubuntu and Manjaro plasma anyway) in a VM guest.
Install the package plasma-wayland-session. Log out. At the bottom of the default log in screen, there's a menu called "Desktop Session". Select Plasma (Wayland) there and login. As a precaution, you should turn off automatic login until you verify it works correctly.
If it all works in the GUI, run Login Screen (SDDM). On the Advanced page change Auto login to reflect the Wayland session.