Thanks for the welcome!
Yes, that's what I followed. Unfortunately, this part is the one that's
giving me trouble:
Modify grub.cfg (CBFS)
Now you need to set it up so that the system will automatically boot, without
having to type a bunch of commands.
Modify your grub.cfg (in the firmware) using this tutorial; just change the
default menu entry 'Load Operating System' to say this inside:
cryptomount -a
set root='lvm/matrix-root'
linux /vmlinuz root=/dev/mapper/matrix-root
cryptdevice=/dev/mapper/matrix-root:root
initrd /initrd.img
When I read through the tutorial that's mentioned here, it makes it seem as
if the relevant changes can be made in /boot/grub and will take effect upon
re-boot. Here's what it says: "Simply create your custom GRUB configuration
and save it to /boot/grub/libreboot_grub.cfg on the running system. The next
time you boot, GRUB (in libreboot) will automatically switch to this
configuration file. This means that you do not have to re-flash, recompile or
otherwise modify libreboot at all!"
I thought I did that (as described in my opening post), but no luck. Do I
need to flash the ROM?