GRUB or EFI files might be on a slightly different location or partition, and the motherboard is pausing before it finds the bootloader.
NVRAM boot entries might be pointing to a “wrong” or “extra” EFI file first, causing a delay.
Less likely, but possible: partition alignment or filesystem differences in the EFI system partition that the firmware doesn’t like.
GRUB or EFI files might be on a slightly different location or partition, and the motherboard is pausing before it finds the bootloader.
NVRAM boot entries might be pointing to a “wrong” or “extra” EFI file first, causing a delay.
Less likely, but possible: partition alignment or filesystem differences in the EFI system partition that the firmware doesn’t like.