Comment 5 for bug 1527664

I dug a bit on this.
curtin sets 3 things:
 - GRUB_CMDLINE_LINUX_DEFAULT : this is what people are most likely to be bothered by.
 - GRUB_DISABLE_OS_PROBER=true
 - GRUB_TERMINAL=console

grub somewhat manages GRUB_CMDLINE_LINUX_DEFAULT via 'ucf' and 'debconf' [1].
So what I'm thinking right now is that the right thing for us to do is
edit the setting in /etc/default/grub directly for GRUB_CMDLINE_LINUX_DEFAULT.

To my reading and understanding, it does not handle modifications we
are making.

[1] https://git.launchpad.net/ubuntu/+source/grub2/tree/debian/postinst.in#n375