I disabled the SecureBoot, booted with Live USB and used the Boot Repair again. This time I unticked "SecureBoot" under Grub options because I disabled it prior to my Live USB boot as I said. I ran the rest of the default advanced options, and I got this:
Oh, I think I shouldn't forget to note that I also got the below terminal message towards the end of boot-repair run.
An error occurred during the repair.
Please write on a paper the following URL:
In case you still experience boot problem, indicate this URL to:
Locked-ESP detected. You may want to retry after creating a /boot/efi partition (FAT32, 100MB~250MB, start of the disk, boot flag). This can be performed via tools such as gParted. Then select this partition via the [Separate /boot/efi partition:] option of [Boot Repair].
Creating config file /etc/default/grub with new version
cp: cannot create regular file `/boot/efi/EFI/ubuntu/grubx64.efi': Read-only file system