I'm using Ubuntu with the standard GNOME environment. I'd like to use the KDE desktop, but I don't want to install the apps, I'd rather use the same applications I already have installed for GNOME. Which package installs only the desktop environment without any of the apps that are part of kubuntu-desktop?
plasma-desktop would best fit your needs
Provides the environment for running and managing applications and integrating interaction of applications. It is designed as generic environment for all kinds of desktop applications, not only applications built on the KDE Platform. It integrates best with applications following the standards used by the KDE Platform.
I've used this before and it works pretty good UKubuntizald Tutorial: Ubuntu + KDE Plasma Workspace