I've installed Ubuntu 15.04 on a Google Pixel 2015 Chromebook, but I can't see the Grub menu. At the time when I should be seeing it, all I see is "Booting from hard disk" and there's some distortion at the top of the screen (it would seem like a few rows of pixels) that lasts exactly the time of Grub menu timeout. So it's like the menu is there, but distorted. If I press a key at that time, the boot process is interrupted: it seems to behave like you'd expect the Grub menu to behave, except I can't see anything.
What could be the problem?
My chromebook uses SeaBIOS (http://www.seabios.org/SeaBIOS) to boot Ubuntu.
UPDATE: SOLUTION I am leaving this for those that may encounter the same situation I have. Edit your /etc/default/grub and make sure that the following lines are commented out like so:
#GRUB_HIDDEN_TIMEOUT=0
#GRUB_HIDDEN_TIMEOUT_QUIET=true
Also it's important that these two lines are uncommented:
GRUB_TERMINAL=console
GRUB_GFXMODE=640x480
I have a strong suspicion now that the last line was essential in fixing the problem. Don't forget to run sudo update-grub afterwards.