It should be noted Sony's TVs are different than their game consoles in what they collect and do. They run a relatively clean version of Android TV except for "Samba TV", which is yet another piece of show-recognizing (known as ACR) analytics. However, you can apparently decline its privacy policy on initial setup and even disable the APK entirely in settings[1]. (Some people also succeeded in ripping it and other bundled video apps out via ADB)
Even given all that, Sony TVs are probably still the tamest smart TVs out there.
> Don't give it your wifi key and don't put it on your LAN.
It entirely depends on manufacturer but I've heard of some actually seeking out open networks for internet access if you don't configure their Wi-Fi. Some people reported an unconnected TV suddenly prompted to update because the neighbour's wifi was unsecured. If you can, I'd set up a specific SSID with no LAN or WAN access just in case.
[1] https://www.consumerreports.org/privacy/how-to-turn-off-smar...