Earlier quoted context omitted.
I've also noticed that XFCE's handling of hotplug monitors leaves much to be desired, and it also cheerfully ignores my preference of not suspending when I close the laptop lid (so I can use only the external monitor and an external keyboard when I have it plugged into my TV). Close the lid under XFCE and "BEEP!" it goes into suspend mode instead of doing nothing. Fortunately, Cinnamon is just an apt-get away, handle…
Can you elaborate on Xubuntu+Cinnamon? That sounds interesting. I also just noticed that there's an Ubuntu Cinnamon which might be right up my alley as well.
apt install cinnamon
Once installed, I logged out, and then picked Cinnamon from the session selection menu (the little gear near the upper right corner). It comes right up, though it won't pick up your preferences from XFCE.
I hadn't realized there was now a Cinnamon spin - is that still in testing? It's not on Ubuntu's list of flavors.