I use an old Amazon FireTV Stick on an old LG LED TV (semi-smart), and neither of them bug me with such fullscreen ads, unless I opt to watch MX content on Amazon Prime (MX is basically third-party ads-funded free OTT content; Amazon Prime requires subscription, and even its standard subscription has occasional ads for Prime content, though Amazon Prime also has a premium pricing tier for ads-free content).

I don't face such third-paety ads nonsense on Netflix and Disney+ (yet), at least on this old FireTV and old LG TV.

Unskippable irrelevant annoying ads and privacg concerns are the main reasons I still steer clear of "smart" TVs.