>the burning answer is really, by the time you've chosen a modern merchant soc, and put a screen on it, you're really more or less at the same BOM cost as a very low end android device (and frankly, the soc bsp you chose is likely to be android/aosp to begin with)

This is, incidentally, also almost universally an answer to "why doesn't nobody make a dumb TV anymore?!"

The off-the-shelf SoC that handle the TV decoding/HDMI bits already has a bunch of general purpose ARM cores; might as well put Android on it instead of writing your own firmware.