on android you can install SoniControl Firewall to "see" the ultrasonics in your house. Try it with all tvs and things off, then try it with the TV on, youtube videos, and so on.

Pixel tracking works better if the TV is connected to the internet. I remember samsung as one of the companies, where, if your TV was not ever given a wifi connection, it would attempt to connect to any open network to do what it needed to do. This sounds unlawful, so i don't know the veracity, but anyhow - if the TV is online, it can just send a half dozen pixels at known locations back home and there is a database of "content pixels at timestamps" and they match the half dozen pixel values to the database and know what you're watching to some degree of certitude.

but for things like dumb panels older TVs and the like, ultrasonics still work.