Your Smart TV is most likely using automatic content recognition (ACR) to spy on your viewing habits.

Vizio
Recent Vizio Smart TVs with SmartCast:
System -> Reset & Admin -> turn off ‘Viewing Data’

Chromecast is built-in so you must deactivate data collection here, too:
Google Home app (on your smartphone) -> Menu -> select your TV from Devices -> click the three dots -> Settings -> turn off ‘Send Chromecast device usage data and crash reports’

Older Vizio TVs:
System -> Reset & Admin -> turn off ‘Smart Interactivity’ or ‘Viewing Data’

Sony
Sony Android TVs:
Settings – Initial Setup -> agree to Sony Bravia policy -> turn off Samba TV

Also go to Settings -> About -> Ads -> turn off ‘Ads Personalization’.

You may also need to go to the Apps -> locate ‘Samba Services Manager’ -> clear cache, force stop, and disable it.

Chromecast is built-in so you must deactivate data collection here, too:
Google Home app (on your smartphone) -> Menu -> select your TV from Devices -> click the three dots -> Settings -> turn off ‘Send Chromecast device usage data and crash reports’

If you own one of Sony’s non-Android TVs you may also check to see if Samba TV is running.

Samsung
Recent Samsung Smart TVs with Tizen:
Settings -> Support -> Terms & Policies -> turn off ‘Viewing Information Services’ and ‘Interest Based Advertising’ and ‘Voice Recognition Services’ (Nuance)

While you are at it, you may also want to disagree to ‘Online Remote Management’.

Older Samsung Smart TVs with Smart Hub:
Smart Hub -> Settings -> Support -> Terms & Policy -> turn off ‘SyncPlus and Marketing’ and ‘Voice Recognition Services’ (Nuance)

LG
Recent LG Smart TVs with webOS:
Settings -> All Settings -> General -> About This TV -> User Agreements -> turn off ‘Viewing Information’ and ‘Personalized Advertising’ and ‘Voice Information’.

Older LG Smart TVs with NetCast:
Settings -> Options -> turn off LivePlus

Roku
Recent Roku TVs:
Settings -> Privacy – Smart TV Experience –> turn off ‘Use Information for TV Inputs’ -> Advertising -> check the ‘limit ad tracking’ box

The same approach should work for Roku streaming players but you cannot completely disable data collection.

Other Android TVs
Other Android TVs do not typically use Samba TV but you can follow the other steps outlined in the above section for Sony Android TV.

This information originates from:
https://www.flatpanelshd.com/focus.php?subaction=showfull&id=1518081245

Links:
https://news.ycombinator.com/item?id=21899491
https://www.zdnet.com/article/fbi-recommends-that-you-keep-your-iot-devices-on-a-separate-network/
https://www.consumerreports.org/privacy/how-to-turn-off-smart-tv-snooping-features/
https://www.flatpanelshd.com/news.php?subaction=showfull&id=1486471312