The problem with those TV apps is DRM. All the major streaming services require that you either use a locked down platform (probably checking SafetyNet and more on Android TV) or settle for their browser UI which lacks dpad support and gets quality throttled to 1080p or lower.

Circumventing that DRM is possible, but no project at the scale of a platform like those would dare the both legal risk and support headache of making those circumventions (which are very liable to break) a core part of the OS.

Kodi (and distros using it like LibreELEC) exist for people who want a FOSS platform for using non DRM encumbered media with a TV remote interface.

Kodi. But it's a mess compared to roku.

Maybe not the solution you were asking for, but the Nvidia Shield on the stock code has been a fair compromise for me. The ads on the main screen are relatively unobtrusive, and sometimes even vaguely relevant to our viewing preferences. We largely watch Hulu, Prime and YouTube+ (with free access to AppleTV and Netflix, but I haven't set those up yet). For ads, we pretty much only deal with Amazon's new advertising in included Prime content. We'll probably stop viewing that content once the series we're currently watching wraps.

For context, my daily driver phone is LineageOS which is rooted all to heck to smack down intrusive advertising and tracking (Magisk, AdAway, AppManager to disable in-app trackers, uBlock on the browser, etc...), and my home network uses a pihole for DNS and malware blocking. I really hate advertisers.

On the pihole, the Shield is actually only the #3 top offender of blocked requests, behind my wife's work laptop and my kid's Steam rig. The main offender on the Shield was the ESPN app, which I removed because I never really watch sports outside of tye idd division game, which most of the time I meet friends out at the local pub anyway. Otherwise the Shield has been a well behaved appliance.

So it's not the perfect ad-free experience, but its hardly the advertising dystopia of broadcast TV.

you could install Android on a raspberry pi with a usb remote.

I’d use a used laptop/desktop on Linux, e.g. something like steamOS, and then use jellyfin to stream stuff to this laptop. The media i watch is pirated, because it is more convenient and better quality than if I stream it through streaming service, even tho I pay for "4k" on these services.