Can a PBP use GRUB?

[tophneal]

Likely. There's a few boards out there that do use GRUB. It doesn't replace u-boot, but is rather used as a stage 2 in bootloading, after u-boot.

Here's a guide from the ODROID forums that might shed some light on getting it set up, though: https://forum.odroid.com/viewtopic.php?t=26894