I have connected second monitor to my laptop and only the external one works, the one on the laptop is just black screen. Going into Setting->Displays only shows the external one, like it's the only one I have.
During booting all the information is shown correctly on the laptop screen, until it reaches login screen, then it switches to the external monitor.
I have no idea what can be causing the problem, it's a new laptop and it was actually all working fine when I turned it on for the first time.
I'm on Ubuntu 18.04