There is only one ARM ISA. Well, okay, multiple (32 vs 64 bit, microcontroller vs unix-capable) but vendors don't change the ISA. (Apple has been allowed to introduce some extension for using a coprocessor (?) recently but that's it.)

The different crap between vendors is just the various onboard devices on the SoC, nothing to do with the CPU cores that implement the ARM ISA.

The "consumer" space is indeed not good, but there's only so many SoC vendors (and most of them rely on Synopsys DesignWare blocks for all the things) and mainline Linux supports most of them really really well.

The real fun time is for us in the BSD world, we're too small for e.g. Rockchip to care about us and contribute like they do with Linux :(

I got my acronyms confused, when I say ISA, I mean the ARM board equivalents of the Industry Standard Architecture[1] that preceded PCI.

[1] https://en.wikipedia.org/wiki/Industry_Standard_Architecture