Is there another box like Apple (Roku?) that can tell your Samsung to go to Art mode?
Not sure how this is an Apple issue, or why you would expect your Apple TV or it's remote to specifically have this control?
I thought if Art mode was active, it senses (motion) and will display the ART, so by turning off your Apple TV and still being in the room one would think the TV should default to Art mode. I will have to try this tonight.