Ubuntu 19.10 doesn't detect second external monitor

I recently got a second external monitor from my Acer Swift 3 laptop running Ubuntu 19.10, however, I have been experiencing problems with detecting it. One of the monitors is connected through HDMI and the other with type-c to hdmi cable. It seems that when starting up the laptop with both monitors being connected, only the one on the HDMI port is detected. The other monitor shows a message that it is connected but not receiving any signal from the computer. When I startup the system with only HDMI monitor connected and then connect the second one, the setup seems to work fine. I tried disabling Wayland in /etc/gdm3/custom.conf and using lightdm, but the problem persists.

Any ideas?

1 Answer

You could try turning the monitor on and off with xset:

xset -display :0.0 dpms force off && sleep 3 && xset -display :0.0 dpms force on

This will turn off the display, wait three seconds and then turn it back on. If this workaround works, this command could be run at startup.

source: Turn off monitor using command line