How to Disable Internal Display from BIOS?

Although it is possible to set HDMI display as primary display from BIOS, the non-exist internal display causes a lot of trouble. Specifically, Ubuntu 17.10 sets internal display as primary display and it is not easy to switch to HDMI display without seeing the desktop content. Also, other Linux distributions like to automatically connect to internal display on boot. Since I don't have a display to connect to the board, how to permanently disable it from BIOS?
I'm using 4G version of Lattepanda.