I only currently get ads when streaming youtube on the TV, even though youtube on my other WAN devices do not get ads. Looking at the pihole logs the TV hits cdn[dot]samsung[dot]com only, so I assume it is proxying YT requests via a Samsung service. Blocking the cdn endpoint disables all internet features, including Netflix, Amazon Prime etc.
Previously, about 18 months ago, the pihole blocked all ads from YT on the TV. So something changed... I don't have the pihole logs from back then otherwise I'd check.
Source: I have a samsung smart TV and run a pihole