boot - Ubuntu booting issue after getting rid of Windows

I used to have Windows and Ubuntu installed on my laptop but I've decided to wipe Windows and just go with Ubuntu. After installing Ubuntu with USB and wiping Windows I've gotten this booting issue.

I've tried reinstalling Ubuntu, having dual installed Ubuntu, and just desperate stuff in general. The error that I get before trying to boot off of my USB is:

Failed to open \EFI\BOOT\mmx64.efi - Not Found
Failed to load image \EFI\Boot\mmx64.efi: Not Found
Failed to start MokManager: Not Found

Current Disk situation from USB non-installed Ubuntu's disk utility:

partition 1

• Size: 537 MB


• Device: /dev/sda1


• Partition Type: EFI System


• Contents: FAT(32-bit version) - Not Mounted

partition 2

• Size: 503 GB


• Device: /dev/sda2


• Partition Type: Linux Filesystem


• Contents: Ext (version 1.0) - Not Mounted

partition 3

• Size: 8.5 GB


• Device: /dev/sda3


• Partition Type: Linux Swap


• Contents: Swap (version 1) - Active

I still have 489GB of free space from the dual boot partition. I'd want to get rid of the partition and just have 1TB Ubuntu but it doesn't even boot.

I've tried boot-repair but still same result.

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This post on itsfoss helped me to solve this problem the most.

This isn't an MBR issue as you are using a UEFI system.

There should be 2 main boot EFI folders with the following paths: a) /boot/efi/EFI/Boot, and b) /boot/efi/EFI/ubuntu. a) should have these files: bkpbootx64.efi, bootx64.efi and grub64.efi. b) should include: fwupx64.efi, grub.cfg, grub64.efi,mmx64.efi and shimx64.efi. mmx64.efi operates Mokmanager and with shimx64.efi is responsible for booting up via a 'Secure Boot'. The Secure Boot option is available in your BIOS. So it seems likely that mmx64.efi is missing with Secure Boot enabled.

First of all I'd go into BIOS and disable Secure Boot, then save settings and see if GRUB menu appears and you can boot from it. If not, then boot up from live flash drive, mount sda1 and check in terminal to see if all 'efi' files are present as well as in the relevant folders as above. If they are there and you weren't able to boot on your HDD then a re-install is probably necessary, but then mount sda2, find your 'home' folder and back it up if you haven't done so. While you're in live Ubuntu I'd give boot-repair one more try. It's not let me down on the rare occasion I've had boot problems.