ironic currently relies on the linuxefi/initrdefi binaries to boot efi entries from grub
those binaries are usually included in the grub2 distribution package
starting from ubuntu mantic, and currently on ubuntu noble, the linuxefi and initrdefi modules have been removed from the grub2 package in favor of using the new linux and initrd loaders
from grub2 package changelog
* New upstream version, 2.12~rc1
* build-efi-images: Drop linuxefi, using new loaders now
unfortunately this means that grub boot entry relying on linuxefi binary does not work anymore on ubuntu noble
this was first observed in Dmitry Tantsur bifrost patch to support ubuntu noble in CI https://review.opendev.org/c/openstack/bifrost/+/928895
looking at the test console logs we can see:
error: can't find command `linuxefi'.
error: can't find command `initrdefi'.
A possible solution for this could be using a fallback mechanism in GRUB.
A similar option is indeed described in the GRUB documentation: https://www.gnu.org/software/grub/manual/grub/html_node/fallback.html
It might be worthwhile just changing the default in the template and not trying to do some sort of fallback configuration dance.
In part because the existing parameters are x86_64 UEFI specific (I think we have a bug about arm64 EFI someplace).
If we can compare with Centos and ensure it boots with whatever streamlined change, I think we'll be good. The major aspect to keep in mind is Grub is likely going to be phased out in the future of the major distributions.