It might stop some depending on the block lists you have. You would have to set a firewall rule to block all other DNS, DoT and DoH servers so nothing can bypass your block lists. Blocking DoH servers is hard because it looks just like HTTPS. Even then, it could still connect to a hard coded IP address instead of doing a DNS lookup.
A better option would be to use an IPS to detect and block suspicious connections from the TV. Ideally, you would just keep it offline though.
I wonder if my pihole would stop this nonsense
It might stop some depending on the block lists you have. You would have to set a firewall rule to block all other DNS, DoT and DoH servers so nothing can bypass your block lists. Blocking DoH servers is hard because it looks just like HTTPS. Even then, it could still connect to a hard coded IP address instead of doing a DNS lookup.
A better option would be to use an IPS to detect and block suspicious connections from the TV. Ideally, you would just keep it offline though.