Comment 7 for bug 2033991

Thanks Leó.

We ran into several problems of this sort while adding deb822 support. I think that's fixed at this point. Do you mind a retest and see if you see the same problem?

In this case the clue is in /var/log/installer/curtin.log:
Command: ['unshare', '--fork', '--pid', '--', 'chroot', '/target', 'apt-get', '--quiet', '--assume-yes', '--option=Dpkg::options::=--force-unsafe-io', '--option=Dpkg::Options::=--force-confold', 'install', '--download-only', 'efibootmgr', 'grub-efi-amd64', 'grub-efi-amd64-signed', 'shim-signed'] Exit code: 100

Another good test here is to try the install offline - all the needed packages should be in place, and either already installed or on the pool. It's interesting that the above were not obtainable in the pool. We did do some seed corrections recently, that may have helped.