We need to have this fixed for 18.10, either via some SRU or via a workaround that we publish in the release notes.
I have investigated a bit on this issue:
I set up two virtual machines with UEFI enabled: one with Lubuntu 18.10 and the other with Xubuntu 18.10.
On vm1 with Lubuntu I did an automatic installation with encryption. After reboot, it ends in the Grub shell.
On vm2 with Xubuntu I did an automatic installation with encryption. After reboot, it just works.
Xubuntu, and I guess also the other flavours, do an installation with an LVM/LUKS container for /, an unencrypted partition for /boot and an ESP.
Lubuntu creates an ESP and an LVM/LUKS container for everything and sets the Grub variables GRUB_ENABLE_CRYPTODISK and GRUB_CMDLINE_LINUX_DEFAULT in the right way. Afaik, this does not match the "official" Ubuntu way to do it and leads to two problems:
- The $ESP/EFI/ubuntu/grub.cfg is wrong
- Important Grub modules are not installed in $ESP/EFI/ubuntu
A possible workaround to boot the encrypted Lubuntu from a live system:
sudo cryptsetup luksOpen /dev/sda2 lukslvm sudo mount /dev/mapper/lukslvm /mnt sudo mount /dev/sda1 /mnt/boot/efi cd /mnt/boot/grub sudo cp grub.cfg ../efi/EFI/ubuntu/grub.cfg sudo cp -r x86_64-efi/ ../efi/EFI/ubuntu/
After a reboot and entering the LUKS passphrase, Lubuntu should start. Maybe there are other configuration issues. And I am not sure, if this will also work with Secure Boot enabled.