I've been happily running a triple boot for nearly half a year with an unencrypted ubuntu 18.04, windows 10, and LUKS encrypted ubuntu 18.04 (not full disk). I rebooted from my unencrypted ubuntu into GRUB and the entries changed. Windows UEFI bootmgfw.efi, Windows Boot UEFI loader, Windows Boot UEFI fbx64.efi, EFI/ubuntu/fwupx64.efi, and EFI/ubuntu/mmx64.efi
were not there before. My encrypted Ubuntu disappeared. Both encrypted ubuntu and windows work fine. I was not messing around with OSes or even installed anything immediately prior to this.
$ sudo update-grub
outputs:
Sourcing file `/etc/default/grub'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.4.0-42-generic
Found initrd image: /boot/initrd.img-5.4.0-42-generic
Found linux image: /boot/vmlinuz-5.3.0-62-generic
Found initrd image: /boot/initrd.img-5.3.0-62-generic
Found linux image: /boot/vmlinuz-4.15.0-112-generic
Found initrd image: /boot/initrd.img-4.15.0-112-generic
Found linux image: /boot/vmlinuz-5.4.0-42-generic
Found initrd image: /boot/initrd.img-5.4.0-42-generic
Found linux image: /boot/vmlinuz-5.3.0-62-generic
Found initrd image: /boot/initrd.img-5.3.0-62-generic
Found linux image: /boot/vmlinuz-4.15.0-112-generic
Found initrd image: /boot/initrd.img-4.15.0-112-generic
Found Windows Boot Manager on /dev/sda2@/EFI/Microsoft/Boot/bootmgfw.efi
Adding boot menu entry for EFI firmware configuration
done
I can mount the encrypted partition and browse files fine on my unencrypted ubuntu. I'm reaching deep into my brain to try to come up with anything I did that could've broke things and I'm coming up empty.