Comment 77 for bug 220961

Installing Kubuntu 22.04 LTS with a 250 MB /boot partition resulted in this message:
installed initramfs-tools package post-installation script
subprocess returned error exit status 1

Decent chance it's the same fundamental issue at work (14 years later?) as it left /boot filled with some symlinks for the initramfs and kernel image that point to nonexistent targets - it probably ran into the size issue while trying to copy in those images.