Thanks, I found a solution, which is a bit counter-intuitive, but which works:

Step 1: Select Devices (I cannot get this to work from Activities)
Step 2: Select the Samsung TV (not the Frame, but some older IR based model)
Step 3: Press and hold the discrete Power ON (not Power OFF) button

This works and shuts down the TV completely. Strange that a long press of the Power OFF does not work, but Power ON does :-)