Hi Thomas,

thanks for the investigative work you are doing.

If someone is testing this with Guix, make sure to actually try to boot Guix
with it (until the root is mounted).  Back in the day I changed the root
discovery of Guix to make it also consider using the entire disk (as opposed to
a partition on it) as a viable root device (see guix master,
commit 9833bcfc08ef009b9e8b4398baa481ef65c80ad7).
That could maybe make it choke if there are multiple partitions/disks with
equal labels (or whatever field it's searching for) on it (though probably not--
as long as its immaterial which of the partitions/disks with the equal field
values is mounted).

FWIW, I'm all for having a MBR-only Guix installer disk as you suggest.
But I'd rather not do the hack the others are doing.  It's hard enough to
debug this stuff when everyone is playing nice.

How should we mount the root when the right way (with two non-overlapping
partitions) boots from DVD ?

(I'm surprised that it needs so much manual intervention to make grub-mkrescue
do the right thing.  One of the reasons I chose grub-mkrescue was that I
assumed that its output would boot fine on many different system types--
it being a rescue disk creator and all.  I guess there are tradeoffs to be
made...)