Walmart's site lets you filter for "Smart = N". Sceptre and RCA are the main brands.
For example https://www.walmart.com/ip/RCA-65-Class-4K-Ultra-HD-2160P-LE...
You could say "I'm not installing software updates" and be safe from ads as long as you don't need any bugfixes, but then you're also missing out on security updates. If you keep it off the internet maybe you're ok, but your TV might start connecting to a neighbor's wifi to give you more advertising.
And with a smart TV, in addition to ads you may also want to be on the lookout for Automatic Content Recognition: https://www.consumerreports.org/privacy/how-to-turn-off-smar...
I'd be much happier just not having a wifi antenna in my television.