Comment by DenisM

For practical fixes, consider replacing the TV with a “commercial monitor” and connecting an Apple TV device instead (or an open source thingy).

Disconnecting “smart tv” from internet to use Apple TV is possible and might work, but you will get nagged to reconnect all the time. And TV mfr will eventually try to find workarounds - purchase access to wireless connections from large-footprint connectivity providers (Xfinity WIFI, 4g/5g networks, etc) or create a p2p network among their own connected devices. I doubt they do it right now as it’s less profitable to focus on niche audience, but eventually it might become profitable enough.