That's not really sufficient. It could still phone home if it falls back to IP addresses. You should be blocking it at the firewall level, not just with DNS.
But me personally, I wouldn't ever connect any of these devices to my network.
The only reason it is on my network is that I need it for home automation (via home bridge). I'll have to see what else I can do.
Firewall rule that prevents the tv from accessing the internet (by mac address if using dhcp, or set a static ip for the tv). Or stick it in separate quarantined IoT subnet with your devices.
Some of these devices also now use DoH to bypass any DNS-level filtering.
It’s still scanning (or at least listening to) all the other devices on your local network, like your phones, PCs, etc. It collects an inventory and if it ever happens to get Internet access, uploads that data.
That's why you put IoT crap into an isolated vlan with its own ssid, enforce device isolation for that ssid across all WAPs, and enforce isolation on the vlan level with your switches to cover any hardwired devices.