The "they use any open wifi they can see" myth has been brought up on HN multiple times, and never did anybody provide any credible proof of this rumour (that started as a single reddit comment).
https://www.techradar.com/news/samsungs-5g-8k-tv-promises-to...
https://www.techradar.com/news/huawei-is-developing-a-5g-8k-...
And to add to this: There has been no proof ever that modern TVs do this, and it would be quite easy for anyone/journalists/reviewers to check this (just run an open wifi and monitor it).
And no, Facebook/Instagram aren't listening to users either, it would need too much bandwidth/server power to process all those conversations, and if you say "they can do the speech recognition on the users' phones", the majority of users use budget phones that don't have that sort of power.
I wonder what's easier to check and verify, a secret government tapping of the Internet, or if the TVs in millions of people's living rooms are trying to connect to open WiFi networks...
You’re right in that this should be easier to find. But I haven’t seen any concerted effort to buy N number of smart TVs and do security analysis on them in order to find something like this.