Get yourself a Nvidia shield. It has no advertisement build in and even can turn on and off the host TV. Also, I would advise you to disconnect your smart TV entirely.
I just have an RPi 4. The protocol that can turn off and on the tv there is just called CEC and you can make simple scripts with cec-client to trigger it. (Kodi also already uses it.)
I have an Nvidia Shield, and ran PiHole for a bit. It didn't block youtube ads for me, but might be regional ranges not being blocked. Eventually I stopped using PiHole since it broke some payment processors at times, and there was no easy way for family members to temp disable it and it became unmanagable.
