It's not that ads are not allowed on TVs. Obviously ads are allowed on TV. It's just that under UK law something has to be very obviously advertisement, part of that is you're not allowed to stick it amongst other things that aren't advertisements.

So in television programming you'll have to have a black screen and then a few seconds of silence before you're allowed to show the first ad. You can't just slam cut into it from a TV show, that's not allowed. Equally if there's a bunch of UI stuff the ads are not allowed to be amongst them because some of them aren't ads and some of them are. It's been that way for literally decades.

What I suspect might have happened is that Samsung tried their luck and then got shut down by the advertising board. Quite possibly they don't have a way to update their firmware. My newest Samsung TV I have access to was purchased in 2019 so there may be a time period after 2019 but before 2024 where they were doing this, but it can't have lasted very long.

There is an incoming law about not adding unremovable bloatware as well, so if they're going to go hard on that as well I can hardly see them putting up with advertising on TV interfaces.