"update-manager -c" Ez nem talál új verziót.
A másik lehetőség:
$ /usr/lib/ubuntu-release-upgrader/check-new-release-gtk
/usr/lib/ubuntu-release-upgrader/check-new-release-gtk:30: PyGIWarning: Gtk was imported without specifying a version first. Use gi.require_version('Gtk', '3.0') before import to ensure that the right version gets loaded.
from gi.repository import Gtk
WARNING:root:timeout reached, exiting