Recovery for failed 4.3 upgrade on step 3

[stage3help]

Another user ran into a similar issue with qubesd and libvirt and they continued from the middle of Stage 3 by manually editing the upgrade script:

Qubes-dist-upgrade stage 3 grub2-efi install failed

Hello! I tried to perform in place upgrade of Qubes OS 4.2.4 to 4.3 today and it failed now my system cannot boot there is no grub menu anymore, I get directly to a grub shell. How can I repair it? How can I get into rescue shell like dom0 shell and repair grub2-efi package? During in place upgrade, grub2-efi failed with error: unpacking of archive failed on file /boot/efi/EFI/BOOT/BOOTX64.EFI;6949ecba: cpio: write failed - Operation not supported no idea why … /boot/efi was writable no pro…