I have re installed ubuntu-desktop. After that Ctrl+Alt+L and Ctrl+Alt+Del shortcuts are not working.
If I click on the button on the top right side of the desktop (where things like logout, switch user and shutdown appear) I can see that lock screen has Alt+L next to it, but its colored grey. If I am clicking from there screen lock and logout are working. But the shortcuts are not working.
gsettings get org.gnome.settings-daemon.plugins.media-keys screensaver
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