It's very hard today to find a competent TV without it having some form of smart functionality. Unfortunately, any device connected to the internet will run the risk of seeing ads serviced by whatever platform they're utilizing. Some manufacturers have decided to build ad distribution platforms from within their operating systems. This can considerably hinder the user's experience, especially in the case of pop-up ads.
When it matters
Ads on smart TVs are still pretty rare today. Not many manufacturers distribute them through their TVs. For the sets we were able to find them on, it's usually a little box you can click to view the contents. Very similar to regular web banner-type ads.
We've only been able to find advertising on Samsung's Tizen-based smart TVs as well as LG WebOS TVs. It shows up in the bottom left corner of the main interface, next to the input and settings icons on Samsung TVs. They can also be seen in the app store. On WebOS, they appear in the LG content Store.
Most manufacturers don't put ads on their TVs. We've only ever seen them on Samsung and LG Smart TVs. Our rating is a simple boolean; if it has ads, it gets a 0. If it doesn't, it gets a 10. We consider banners that are mentioned as sponsored to be adverts as well as anything that isn't related to what you should be seeing (e.g. a car ad on the app store).
If a TV allows you to remove ads without any form of trickery, it passes this test. We don't consider the option of opting out of them to be of equal value as a true ad-free experience. Just allowing you to opt-out of personalized advertising also doesn't pass this test. We have not yet seen a TV with ads that allowed us to disable them completely.
Getting rid of ads
There are ways to block the ads, but they're unfortunately not simple settings you can set on TVs themselves. You have to block them network-wide using more advanced methods such as a custom router firmware and 3rd party ad-blocking DNS servers. These aren't really accessible to most users. Some of the TVs, including Samsung ones, allow you to apply this DNS server from within the TV itself. For more advanced readers that do want to learn about these solutions, here are some methods that can provide ad-blocking over your entire network:
Opt-out of personalized advertising
Some TVs allow you to opt out of personalized advertising. Unfortunately, all this does is show you random adverts instead of ones that are based on data they have of you. We've yet to see a TV that simply allows you to disable them entirely. Samsung is also currently phasing out this option as of software version number 1155.
Many consumers looking for TVs today are interested in smart features since it allows them to cut the cord and consume content on an ad-free platform whenever they want. It's unfortunate that manufacturers have decided to build ad services within their software to compensate for the ever falling margins on TV sales. Some might not mind, but for a lot of people, it might be a deal-breaker.