Comment 4 for bug 2006515

This bug is limited to arm64 systems that have installed the 1.52+15.7-0ubuntu1 version of shim-signed that briefly made its way into the lunar release pocket before being withdrawn, or systems that installed a correspondingly-buggy version of shim-signed from -proposed.

We do not plan to do further work in the packages to address this upgrade path.

You can fix your systems by running the command:

sudo update-alternatives --remove-all shimx64.efi.signed

and then repeating the upgrade procedure.

I note that the logs in comment show this problem persisting even in the case that shim-signed is a new package - i.e. alternatives were not cleared on package removal. It looks like there is still a bug in the current package, that alternatives are not removed on removal of the package, but should be. Removal of shim-signed is an unlikely action during ordinary operations, so the severity of this is not high, but assigning this bug to Julian to take a further look.