> I'm sometimes surprised at the plethora of cheap handheld gaming systems coming out of China that support either Linux[...]

Do you have examples?

All the ones I see that "support Linux" are locked to a single kernel build, and so aren't much better than a hacked Android ROM, which is because the SoC manufacturer makes a "sort of working" version and dumps it over the wall, and this is exactly the same thing they do with the crappy Android phones which are never mainlined.

There are massive projects to bring all of these in mainline such as SunXi, which makes AllWinner look supported even though they actively work against it.