In the Privacy tab, you can specifically select a "block of rules" for Samsung devices. Also, EasyList will block a lot of requests.
Unfortunately, NextDNS will not show from what device a blocked request came unless you give it a name in the app, and of course there is no NextDNS app for Samsung TV's. Some suspicious domains I see often in my logs:
samsungads.com
tvx.adgrx.com
samsungcloudsolution.net
But, in short, I have loaded NextDNS with the most common blocklists (EasyList, Anudeep etc.) and added the "Samsung" list. Result is: no ads anywhere on my 2018 smart tv.