Why? Just don't connect it to the internet.
(Yeah, yeah, when someone actually demos a TV seeking open WiFi APs, then we'll talk. And anyone bringing up ETH over HDMI gets a spankin'.)
XFinity has some bullshit where your router provides an AP for other XFinity members.
My understanding is that it uses bandwidth you aren't paying for to carry this signal rather than using up what you paid for, but still it's been there for something going on ten years.
There are reports, including in this thread, of TV models that require a login to proceed during initial setup