"Dual-screen is broken on Pinebook - will be eventually fixed with kernel update. If you want to use HDMI without LCD do 'xrandr --output HDMI-1 --off; xrandr --output eDP-1 --off; xrandr --output HDMI-1 --auto'. To enable LCD back do 'xrandr --output HDMI-1 --off; xrandr --output eDP-1 --off; xrandr --output eDP-1 --auto'. If xrandr is not installed do 'pacman -S xorg-xrandr'"
I have a temporary solution I've been using on a different machine.
This is to toggle, but it could be adapted to do dual screen automatically.
Most recent release at the time of writing https://github.com/anarsoul/linux-build/releases/tag/20190112 states the following.
"Dual-screen is broken on Pinebook - will be eventually fixed with kernel update. If you want to use HDMI without LCD do 'xrandr --output HDMI-1 --off; xrandr --output eDP-1 --off; xrandr --output HDMI-1 --auto'. To enable LCD back do 'xrandr --output HDMI-1 --off; xrandr --output eDP-1 --off; xrandr --output eDP-1 --auto'. If xrandr is not installed do 'pacman -S xorg-xrandr'"
I have a temporary solution I've been using on a different machine. This is to toggle, but it could be adapted to do dual screen automatically.
https://gist.github.com/wodend/3f8b3cec65f07c09ae3a8b7b704935b5