Connect it to the network to let it talk to local devices but block it from connecting to the internet.
That should still let you control the TV from your phone via the LAN, or if you have a HomeAssistant server, it will be able to control it.
Yeah, I have been doing this with a naive firewall rule blocking its IP from egress, but how long until they'll wise up to it and start truly nefarious shit like using hidden MACs to acquire multiple addresses in the background? Then you could probably VLAN it off, but most people don't have managed gear on their networks.