I have a Lenovo Idea-pad running 18.04. It is connected to a Samsung TV with a HDMI cable. On booting the laptop the TV mimics the computer screen until the login screen which comes up on the laptop but not the TV. When I log in to the laptop it goes where it should but the TV just shows the beaver background. Has anyone any idea what is happening? PerlDuck suggested Windows key+P . It works!