Oh, and Apple's NVMe interface is non-compliant. This is widely reported as Apple locking Linux out with the T2 chip, but that's not really true. The T2 chip will by default prevent unsigned kernels from reading/writing to the SSD, but this can be disabled.
Even if it's disabled, the controller is not standards compliant, and Linux won't see the underlying block device. I saw some diffs floating around on github a few years ago that fixed it, but I don't think it was ever mainlined.
Basically, post-2016, Apple seems to have incorporated even more custom (and undocumented) hardware that running alternative OSes on them is basically impossible. Windows works because of the Apple-provided HAL + drivers for WinNT.
As far as I know it’s only available on Apple OSes.
Which is unfortunate, because the 2015 models make great Linux machines.
The introduction of the T2 chip made proper Linux support much harder to achieve.