Earlier quoted context omitted.
Mobile hardware is a nightmare. The best thing we have to cope with it, so far, is libhybris. And I don't see things getting much better. All we have is Pyra, the incoming Neo900 and semi-closed Jollas with Sailfish.
There's a "collaborative project to unify the Hardware Abstraction Layer for projects which run GNU/Linux on mobile devices with pre-installed Android" called Halium. https://halium.org/
Thanks, but no thanks.