Failed to open \EFI\Microsoft\Boot\grubx64.efi - 80000000000000E

Solution 1:

Boot Repair will sometimes copy GRUB to other filenames, including those that are normally used by Windows.

You didn't say whether you're able to boot normally after those errors appear, but your Boot Repair output makes it look like you can; specifically:

=================== efibootmgr -v
BootCurrent: 0001
Timeout: 0 seconds
BootOrder: 3003,3001,3004,2001,2002
Boot0000* Notebook Hard Drive   BIOS(2,500,00)................-.`.......`.A.`........................................
Boot0001* ubuntu    HD(1,800,100000,3c6d1212-54d5-4b03-8eb6-680c74425f10)File(EFIubuntushimx64.efi)
Boot0002* Internal CD/DVD ROM Drive BIOS(3,500,00)................-.g.......g.A.g........................................
Boot0003* Windows Boot Manager  HD(1,800,100000,3c6d1212-54d5-4b03-8eb6-680c74425f10)File(EFIMicrosoftBootbootmgfw.efi)RC
Boot0004* Ubuntu    HD(1,800,100000,3c6d1212-54d5-4b03-8eb6-680c74425f10)File(EFIubuntugrubx64.efi)RC
Boot2001* USB Drive (UEFI)  RC
Boot2002* Internal CD/DVD ROM Drive (UEFI)  RC
Boot3001* Internal Hard Disk or Solid State Disk    RC
Boot3003* Internal Hard Disk or Solid State Disk    RC
Boot3004* Internal Hard Disk or Solid State Disk    RC

This is the output of sudo efibootmgr -v. Don't freak out over it; you can ignore most of the long scary hexadecimal numbers. Pay particular attention to the BootCurrent and BootOrder lines. The BootCurrent line tells you how the OS booted -- in this case, by using the Boot0001 option, which you can see is for Ubuntu. The BootOrder line, however, indicates that the computer is configured to try several other options before that one. These are default boot loaders -- normally EFI/BOOT/bootx64.efi, but it's entirely possible that your computer uses EFI/Microsoft/Boot/bootmgfw.efi for some of these. My hunch is that Boot Repair copied GRUB to one or both of these locations, but with Secure Boot active, GRUB won't launch without the help of Shim (shimx64.efi). Hence your error messages, which I'm guessing come from your firmware.

The most puzzling thing about this is that you booted via the Boot0001 (Ubuntu) entry despite the fact that it's not on the BootOrder list. Maybe your firmware goes off-list when nothing else works, or maybe it's actually on the list but is not being reported by efibootmgr for some reason.

In theory, you should be able to overcome this problem by typing the following command in Linux:

sudo efibootmgr -o 1,3003,3001,3004,2001,2002

This changes the BootOrder line to be what it is now, except with the working Ubuntu entry first. I'd try this before deleting any files. If this doesn't work, though, go ahead and rename the EFI/BOOT/bootx64.efi and/or EFI/Microsoft/Boot/bootmgfw.efi files, or the directories in which they reside. If you can boot after renaming these files or directories, go ahead and delete them. If renaming them makes matters worse, you can use an emergency disk to rename them back to their original names.