I haven't done any UEFI installs for a while, but, if you want to look into it further, you might want to look into the man page for efibootmgr. While you can copy files into /boot/efi from the installation disk, you need to tell the UEFI bios what its looking at. This might be different since I last played with it. My ASUS UEFI bios dates from 2011, and I believe it was 2014 when I last put siduction on that computer. Hopefully, it's easier to deal with now. Heh, I've been hoping for a workable CoreBoot for a long time.