/dev/root does not exist trying to run installation on MacBookPro8,2 with both Qubes R3.1 and R3.2

[Tobias Abenius]

Dear all,

When I'm trying to boot Qubes on my MacBookPro8,2 from ca 2011 using the
steps

1. put qubes on USB-stick using dd
if=Downloads/Qubes-R3.1-x86_64/Qubes-R3.1-x86_64.iso of=/dev/disk2 bs=100m
2. reboot
3. in the previously installed refind choose either xen.efi or the penguin

if I boot using xen.efi the graphics will be distorted beyond
comprehension, possibly incorrect screen width / offset, maybe I see an
extremely flat skewed penguin

if I boot using the vmlinuz option I get the errors
dracut: Scanning for all btrfs devices
dracut Warning: /dev/root does not exist
I re-ran with the rd.debug option, dropped into a shell and saved the
rdsosreport.txt for R3.1 (found at
https://github.com/QubesOS/qubes-issues/files/465676/rdsosreport-2.txt )

I also tried with the current R3.2 and get the same error, see attached
rdsosreport.txt.
[ 198.509872] localhost dracut-initqueue[527]: Warning: Could not boot.
[ 198.510379] localhost dracut-initqueue[527]: Warning: /dev/root does
not exist

Is there anything I can do, is it possible to install Qubes in another
way, by hand even?

Thankful for your time, Tobias