It seems to have stabilized after a couple of hours under power. There are frequent video flickers but no more lengthy black screens. And, the unit is only slightly warm after being powered for a couple of hours. Now that it appears stable, I want to try it on a different HDMI input - the one that originally gave me the Not Support! screen.
I think I need to disable gestures on my keyboard as I am occasionally surprised by a change of scene (or screen).
The keyboard/touchpad functioned from the get-go, with no need to install drivers, and once things started to stabilize, it was remarkably simple to setup WiFi, set the time zone, etc.
As for WiFi range, it has the same path to the router as the TV itself but the connection is only half as good. One suggestion on the forum was that Wifi range was better using a hub and wired keyboard/mouse. For now, it seems adequate but I might try using a short cable to move the wireless USB dongle away from the unit.