You wrote:
When I tried going into the UEFI configuration menu
You did not specify how you tried entering the UEFI configuration menu, though. There are several ways to do this, including the following:
- Boot-time keypress -- Most computers provide a keypress to enter the firmware setup utility. The most common options are Delete, F2, and Enter; however, there are others, and the key varies from one machine to another. Sometimes this is very finicky or won't work at all if the firmware's "fast start" option is enabled (or equivalently, if it's set to do minimal USB initialization).
- Boot manager option -- Some boot managers, including GRUB and my own rEFInd, can optionally provide a menu entry to boot to the firmware setup utility. The way Ubuntu configures its GRUB menu, this option is absent by default. I haven't verified ravery's solution, but it looks correct as a way to enable it. IIRC, Boot Repair will also do so. If you were to install rEFInd, or launch it from a USB drive or CD-R, its option to do this (a second-row icon that looks like a stylized computer chip) should be present by default.
- OS reboot-to-firmware option -- On recent versions of Ubuntu (those that use
systemd
), typing sudo systemctl reboot --firmware
should reboot into the firmware setup utility. Windows 8 and later provide similar functionality; see here for details.
Note that the last two methods depend on the firmware supporting this feature, so they won't work on some computers. The error message you report sounds as if your firmware might not support the feature, but if you've entered the setup utility in the same way you're doing it in the past, that doesn't seem likely. In any event, I'd try one or both of the other methods that you're not using.
If you continue to have problems, then it could be that your NVRAM's contents have been damaged. This can sometimes be repaired by resetting the firmware to its defaults and/or by applying whatever firmware update may be available. Unfortunately, this creates a chicken-and-the-egg problem, since you must normally enter the firmware setup utility to reset its options or update the firmware. In an extreme case like this, you might use a fourth method:
- Unplug all boot devices and power up -- If you turn off the computer and unplug all the disks and other bootable devices (which might include Ethernet cables on some networks), then when you power on the computer, it will find nothing bootable. It will normally go into the firmware setup utility at this point. The drawback is that some computers will then forget all their previously-working boot entries, so when you plug the disk back in, it might no longer boot, or it may boot straight to Windows, bypassing GRUB. Still, this method can be a useful last-resort option. (You can re-create the Ubuntu/GRUB boot entry in various ways, if necessary.)