S905X is a SoC and the drivers are there. You don't sell SoCs these days without providing Linux drivers or giving access to specifications.
So the main difference between those boxes is the remote control.
The remote may be the major difference between boxes from different sellers/manufacturers, but the issue here is with the chipset manufacturers/designers, ie. Amlogic and the like.
Afaik they only release drivers and software for a really old kernel and they only seem to care about android (I could be wrong, but that's my understanding of the situation)