Hi guys, have a problem with screen after locking. I have laptop with main screen and external display connect via HDMI. When I lock the GNOME both screens going to ‘standby’, but than after few seconds second screen display messages ‘no signal’ and than ‘entering power saving mode’ and this action turn on both screens: they black but still on (meaning not in standby mode).
If you have the nvidia GPU it can cause this since by default the nvidia GPU drives the hdmi port and the IGP drives the built in screen so some have the same issue you are seeing.
Searching this forum for problems with suspend gives several potential fixes.
Same situation when screen goes blank after time interval. Both displays stay blank than external goes to ‘powersaving mode’ and awake both. Cyclic situation.
The only thing I can think of from that is you are using wayland.
Have you tried using xorg to see if the fault is wayland by chance?
If not, then please do. It is possible the issue is in wayland itself and trying xorg would help narrow down the cause. If it still occurs in xorg then it is a little deeper.