Comment 14 for bug 1872212

Same here as Alex (a-t-page) and Night Train (nighttrain).
But with another Ubuntu on a different drive and partition:

Setting up grub-pc (2.04-1ubuntu26.7) ...
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.4.0-53-generic
Found initrd image: /boot/initrd.img-5.4.0-53-generic
Found linux image: /boot/vmlinuz-5.4.0-52-generic
Found initrd image: /boot/initrd.img-5.4.0-52-generic
Found Windows Boot Manager on /dev/sdb2@/EFI/Microsoft/Boot/bootmgfw.efi
Found Ubuntu 18.04.5 LTS (18.04) on /dev/sdb5
Adding boot menu entry for UEFI Firmware Settings
done
Setting up software-properties-qt (0.98.9.3) ...
Setting up grub-efi-amd64-signed (1.142.9+2.04-1ubuntu26.7) ...
Installing grub to /boot/efi.
Installing for x86_64-efi platform.
grub-install: warning: Internal error.
grub-install: error: failed to register the EFI boot entry: Operation not permitted.
Installing grub to /boot/efi.
Installing for x86_64-efi platform.
grub-install: warning: Internal error.
grub-install: error: failed to register the EFI boot entry: Operation not permitted.
Installing grub to /var/lib/grub/esp.
Installing for x86_64-efi platform.
grub-install: warning: Internal error.
grub-install: error: failed to register the EFI boot entry: Operation not permitted.

System:

lsb_release -d
Ubuntu 20.04.1 LTS

Operating System: Kubuntu 20.04
KDE Plasma Version: 5.18.5
KDE Frameworks Version: 5.68.0
Qt Version: 5.12.8
Kernel Version: 5.4.0-53-generic
OS Type: 64-bit