sk00b wrote:

EFI problem

What is the problem, exactly? Use <ctrl>+<alt>+F4 to see any error messages from the installer in full.

I will take a stab in the dark and guess that the system won't boot after installation?

If that is the case then use the "expert" installation and select "force extra installation to the EFI removable media path" in the GRUB options.

For an already installed system use rescue mode to obtain a shell in the installed system then run

dpkg-reconfigure grub-efi-amd64

^ That should also offer the option described above.

Alternatively copy /EFI/devuan/shimx64.efi on the EFI system partition to /EFI/Boot/bootx64.efi and also copy /EFI/devuan/grubx64.efi to /EFI/Boot/ (all locations given relative to the ESP, which should be mounted under /boot/efi/ in the installed system).

If you use the last method then be sure to update the debconf database after booting into the new system:

# debconf-set-selections <<!
grub-efi-amd64 grub2/force_efi_extra_removable select true
!