My TV turns into this if I set it behind a pihole and block all requests to it. I have heard some TVs will look for open networks (or known ones with deals such as xfinity) but there are none around be that I'm aware of and it responds as if it is dumb other than the features that can be turned off like frame interpolation. But those do randomly reset themselves which is quite frustrating.
The key is block all network access. A lot of IoT devices have hard coded DNS so even running a pihole will sometimes not work.
Don't forget the sleep timer. Such a simple QoL improvement, and none of the TVs I've owned in the past 10-15 years have had one. Seems like every TV had it when I was a kid (or at least a good sized portion did).