Using KDE in Qubes templates / app VMs is possible. Here are steps for getting it working:

1. In dom0 make a clone of a debian-13 template (which is Gnome-based):

2. In the new template run sudo tasksel then select "KDE" and de-select "Gnome".

3. After tasksel is finished installing KDE, run sudo apt autopurge gnome* to remove Gnome – this is important.

4. Add a file to the template's /etc/profile.d to set the required desktop session variable:

   $ sudo nano /etc/profile.d/kde4qubes.sh
   

The content of the file:

export XDG_CURRENT_DESKTOP=KDE

1. Create a link in /etc/xdg/menus. This allows apps like Dolphin to associate file types:

   $ sudo ln -s /etc/xdg/menus/plasma-applications.menu /etc/xdg/menus/applications.menu
   

2. Shutdown the template.

3. Change template and appVM settings under the "Applications" tab to include the new utilities. Adding "Open file manager" and "Run terminal" will run the default file browser and terminal (in this case, Dolphin and Konsole) assigned for the template's environment, but you can also add "Dolphin" and "Konsole" as app entries to access them directly.

4. (Optional) Run Dolphin and under "Configure Dolphin -> Context Menu" de-select the "Send file via KDE Connect" plugin. This will prevent Dolphin from freezing for 30sec when you first access a file's context menu. (It would be preferable to configure KDE Connect to prevent this delay... suggestions are welcome!)

These instructions can probably be adapted for Fedora templates as well with some changes to the tasksel and apt steps. They may also work when starting from an Xfce template; in that case the 'autopurge' step will be very important for removing the Xfce environment settings as simply removing the packages doesn't work.