Score:0

External monitors don't stay off when screen is locked in 21.10

us flag

I have an Intel NUC PC with two external monitors. With Ubuntu 20.04 LTS, when the computer is inactive for several minutes, the screen would lock and the displays would turn off. Ever since I upgraded to Ubuntu 21.04, and now Ubuntu 21.10, this no longer happens. The screen will lock after 5 minutes of inactivity, but the monitors never turn off. Either the lock screen displaying the time stays visible forever, or the display becomes black but is still on (with just the cursor visible). I know that Wayland has become the default since Ubuntu 21.04, so I'm wondering if that has anything to do with it.

Can be easily reproduced by locking your screen by pressing Super+L. In my case, the screen locks and the displays are turned off, but 3 seconds later the displays are turned on again with the lock screen visible. They won't turn off after that. They should stay turned off.

How do I make my displays turn off when the system is locked?

UPDATE:

As suggested by chrismou, I tested to see if the same issue occurs with Xorg. The same issue happens with Xorg, so it has nothing to do with Wayland.

cn flag
You could test to see if it is Wayland related. On the log in screen, under your name click "Not Listed" and click the cog that appears bottom right of the screen. Select Ubuntu on Xorg, log in as normal, then wait and see if that "fixes" it
us flag
Same issue happens in Xorg. I've updated the question to better describe the issue.
Score:0
us flag

This is going to sound ridiculous, but I resolved the issue by switching around the cables used to connect my monitors. As explained earlier, I have two monitors attached. Monitor one is connected via a DP cable, and monitor two via an HDMI cable. I simply switched around the cables; so monitor one via HDMI, monitor two via DP, and now the issue is resolved.

What's even more crazy, this also fixed another very annoying issue I was having. GNOME Shell would not remember the window positions after the screen was locked. Whenever the screen was unlocked, all windows were moved to the same workspace, requiring me to rearrange my windows every time I log back in. Simply switching the cables resolved this issue as well.

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