I found the solution to this bug, and was able to successfully install a
testing live image and boot it. The problem is actually in the
calamares-settings-debian package.
The problem is caused by changes in the syntax of an upstream Calamares
configuration file. Calamares has a mounts.conf which mounts additional
filesystems needed for the chroot to work correctly, like /sys, /dev, and
/proc. This file includes a way to indicate that filesystems should only be
mounted on uefi systems, and this has changed.
IN the old config syntax, there were two groups of filesystems, "extraMounts:"
and "extraMountsEfi:". In the new config syntax, "extraMountsEfi:" was removed,
with all filesystems instead being listed under "extraMounts:". An additional
key value pair is added to each entry which must be mounted for uefi systems
"efi: true".
After deleting extraMountsEfi from mounts.conf on the live image, and adding
"efi: true" at the end of the file in the "efivarfs" entry, the install worked
with an efi variable being created in my firmware.
The file that needs to be updated is in the calamares-settings-debian package
"calamares/modules/mount.conf". The file containing corrected syntax in
upstream calamares is "src/modules/mount/mount.conf". It may be worth
synchronizing the other changes in this file as well.
