Doesn't surprise me; Apple for not doing anything by standards. When you control all the hardware, I guess it doesn't matter. You can have broken ACPI and driver implementations all over the place.

I've started to give up on ARM embedded boards for the same reason. You need to build out images for all the different potential ARM systems if they don't use device trees. There are Intel Atom/AMD Geode Pi/Beagelboard clones that will boot up just like a desktop and you can install most Linux distributions right on them without modification.

If ARM ever decides to start selling an architecture spec instead of just a SoC spec, I think it would go a long way at making it a better platform. I'm pretty sure Apple would still ignore it f

Its happening (slowly) SBSA/SBBR/etc are out there and being implemented. Its just taking a while for EDK2/linux/etc to get to the point that it can run on a random ARM SOC. Once that happens though, suddenly you have a machine that can install off the shelf linux distros. Right now, There are only a couple systems that work like you would expect (mostly AMD Seattle machines, although there are a couple others) but over the next few years I would expect that the firmware guys to start expanding the device compatibility.

Eventually (particularly with ACPI) it will become apparent to the ARM ecosystem, that they can make their devices compatible with the standards, or they can spend millions on engineering effort to build their own firmware/OS stacks that will perpetually be behind the capabilities of the rest of the ecosystem.

NVMe added feature of HMB (Host Memory Buffer) to use host DDR rather than internal RAM. So, I think this chip used HMB feature.

It's presumably not standard Host Memory Buffer, since the spec says "The controller shall function properly without host memory resources."

It's not as though they are manufacturing these for anybody else to use.