Boot from local drive is an isolinux option (i.e. non-EFI), I think it needs the OS to have been previously installed in BIOS mode, not EFI.
a new ISO is on the way, monsta found a better way to ensure /etc/default/grub didn't go missing. We'll get live-installer to purge grub-pc first, before installing grub-efi-amd64.
'boot local disk' doesn't seem to work in the live grub menu, end up at boot> prompt. Normal boot works fine.
- live-installer eject mechanism removed. We still won't see the eject message in plymouth, but this should get rid of the reboot bug and the squashfs errors.
- debian-system-adjustments sets "quiet splash" in /etc/default/grub.d, so it no longer matters if /etc/default/grub goes missing. This should fix the plymouth theme post-install in EFI mode.