I have a Lenovo ThinkPad X1 Carbon 4th Gen.
Recently few days ago I got an update, in that update I was unable to find the option to enable backlight in settings > power options.
Where It was available before the update.
Please check the issue.
Thanks for providing a good distro & Thanks of support in advance.
Is it a laptop keyboard or external keyboard?
Please post your system info as outlined here: