So, I've successfully installed Ubuntu to the eMMC and when I power up, it boots right into it. But try as I may (and I have tried!), I can no longer get to the Front Page or the EFI shell. No matter how hard I pound on Escape at the initial prompt, it goes ahead and boots GRUB. The screen I see is the GRUB screen. Note that if I don't pound on Escape, then it skips the GRUB screen and boots right into Ubuntu. From what I've read here, you can fix this by removing the RTC battery. But surely, there's a better way?