Happening to me on HP EliteBook 8460p UEFI install and Ubuntu MATE 20.04! Tried all sorts of GRUB_TIMEOUT and GRUB_TIMEOUT_STYLE settings to no avail.
GRUB menu *IS* actually there but it won't show up: it just freezes on a black screen until the timeout expires or a key is pressed.
Happening to me on HP EliteBook 8460p UEFI install and Ubuntu MATE 20.04!
Tried all sorts of GRUB_TIMEOUT and GRUB_TIMEOUT_STYLE settings to no avail.
GRUB menu *IS* actually there but it won't show up: it just freezes on a black screen until the timeout expires or a key is pressed.