Since Boot Repair doesn't seem to have worked, the next option is my own rEFInd boot manager. It can boot a Linux kernel directly and needs little or nothing in the way of configuration files (unlike GRUB, which requires a very complex configuration file, which is what's not working for you). Download a USB flash drive or CD-R image from the rEFInd downloads page, prepare a boot medium, and try booting it. (You'll probably have to disable Secure Boot, if you haven't done so already -- your Boot Repair output indicates it is disabled, but you may have re-enabled it.) rEFInd should show you options to boot both Windows and Ubuntu. (For Ubuntu, rEFInd will likely show options for both GRUB and direct boots of your kernels.) Try them both. If any of the Ubuntu options works, you can install rEFInd via its PPA or Debian package and you should be good to go. If rEFInd fails, post back with details of what went wrong.
EDIT: Oh, wait, I just noticed that you're using XFS. That will complicate things with rEFInd. Pete Batard's EFI driver package includes an XFS driver. You could add that to the rEFInd USB flash drive and it might work, but I make no promises about that. Switching to ext4fs or Btrfs would give rEFInd a better chance of working, but of course that will require re-installing.
If you do re-install, do so in EFI mode from the start. Installing one OS in EFI mode and the other in BIOS mode is an exercise in pain. Your Windows is in EFI mode, so you should install Ubuntu in EFI mode, too.