Like many other Sony Bravia televisions, it is very difficult to get and maintain a signal from NVIDIA graphics cards at 120hz. It’s very important that RTINGS.com covers these kinds of issues.
Older drivers help a little, as does setting the TV HDMI signal to Enhanced (VRR), but ultimately it’s a dud for PC usage until Nvidia or Sony address the issue.
Unfortunately we’re not aware of any way to replicate the same experience as art mode but while watching slideshows on YouTube. Sorry about that. You could try contacting Samsung though, to see if they can offer any insight!