24: Lock screen never suspends monitors

[AutoDMC]

Hello!

I have an Apple Studio Display as my primary monitor*, and as such I don't have a power button available. When it's time to go to bed, I like to lock my computer, as with MacOS and Windows this will allow the monitors to go to sleep pretty quickly (and if not, I press "escape" and the monitors sleep). Then I unlock the next day and move forward, leaving my computer running all night to think deep thoughts.

On Ubuntu 24, however, when the screen blanks, it just draws black pixels across the monitors, but both monitors (the Studio and my Acer 1440p monitor) stay powered on all night.

I've tried setting the blank screen delay, which works on the desktop. The screen fades after the time limit and then the monitors go to sleep.

However, the monitors never sleep on the lock screen.

Short of setting the screen blank delay to something tiny when going to sleep, or waiting for the 10 minute timer to tick by... how do I tell the lock screen to behave like the desktop and suspend the monitors?

(* I got the Studio Display when my daily driver was my MacBook. I upgraded to a nice PC with Ubuntu, but still want to use my needlessly expensive monitor.)

[currentshaft]

The screens do not turn off because the system is only locked, not suspended.

Check the Power tab in Settings, you should be able to adjust it accordingly.

"systemctl suspend" is also a command you can use to suspend the system immediately.

[AutoDMC]

That is very true, yes! However, I want the computer to stay operational; I have stuff running overnights usually. If there's nothing running overnight, might as well turn the computer off. But this is a case where I might have some long running task going, and I want to keep the computer online and running, but I want to be able to have my monitors shut off because I'm on a lock screen.

Again, worst case I can switch the blanking time to something low and/or just wait 10 minutes for the monitors to blank, while leaving the computer unlocked.

Preference, though, is I can lock the computer, leave it running on whatever I'm doing, and have the monitors shut off.

I've done some research, but I don't know what state Ubuntu is in when it's locked; I don't know if there's some other state that needs to be told it can blank.

[currentshaft]

I just tried "xdg-screensaver lock" on my Thinkpad laptop and it locked the screen and turned my screen (OLED) off. You're saying when you do this, external monitors remain backlit?