Discover will report an available UEFI Secure Boot firmware update, but can't install it and doesn't offer any guidance as to how to install manually.
If you try to install with Discover you get "THE INPUT IS NOT OF CABINET FORMAT".
Since Discover is advertised as being the central place to install & update software, it should ideally handle this or at least give guidance as to how to resolve.
I found that the following installs the update - at minimum Discover should tell the user to do this:
sudo fwupdmgr refresh
sudo fwupdmgr update
Then reboot when requested.
Linux/KDE Plasma: Kubuntu 22.04 LTS
So `sudo fwupdmgr update` works? Or does that fail too?
sudo fwupdmgr update worked for me.
This bug also affects me. It seems that it was reported recently in many places, e.g.:
On laptop Samsung NP670 there is another error message: "failed to write data to efivarfs: Error writing to file descriptor: Invalid argument". I can also confirm that the problem with "THE INPUT IS NOT OF CABINET FORMAT" can be seen on HP desktop PC UEFI update.
Pretty sure it's the same issue. Somebody who can reproduce, please try fresh 5.27 branch and report back if the issue is not indeed solved.
*** This bug has been marked as a duplicate of bug 468379 ***