I have a nearly-dumb TV (chosen for that and never connected to the Internet) and a separate little Android TV box I got from AliExpress for 25 bucks were I only use Kodi.
The TV is maybe 4 years old, the little box maybe 1 year (I had a 10 year old similar thing before but it can't handle newer video formats so I switched).
Have yet to see a single Ad.
Mind you my setup is as is because I've long ago learned that you want your fast-changing-cheap-tech bits separate from your expensive-long-life stuff, so in this case I want my digital video file decoding hardware separate from the much more expensive large digital TV screen so that I can switch the former without paying a new of the - much more expensive - latter.
Here's the GitHub repo of a software developer that was one of the first to find this, and I think the first to make it really public. It has some info on how to tell and possible steps to do some cleanup.