I did this to disable the "Samsung TV Plus" app that is impossible to uninstall, and otherwise impossible to stop from periodically taking over the TV (e.g. instead of booting to the last app that was opened or last HDMI input, it starts its own app instead, or after Netflix has gone idle for awhile, it switches to its own terrible channels).

I blocked every Samsung domain that I possible could in a fit of rage.

Now, instead of getting some random jarring channels when I turn on the TV (or.. random times), at worst it's a black screen that says "something went wrong" and I open the thing I want. The TV just slams the pihole with failed DNS requests over and over.