Lock screen without blank in 18.04

I'm running Ubuntu 18.04 on a laptop. When I lock the computer, I want the screen to remain on indefinitely. I do want the computer to lock automatically when it is idle (but still, the screen should remain on).

First I tried in Settings -> Power to set Blank Screen to never, but that did not work. I have tried the suggestions from others who asked the same question here, but they are for different versions of Ubuntu and none of them worked for me.

Does anyone know how to fix this problem in 18.04?

When you lock your screen manually with Super + L just hold it a bit longer, then the screen will not blank immediately. It blanks after the time interval you set at Settings > Power > Blank Screen.

Edit: I tested it once again (this time it was chaging) and the screen did not blank when I locked my PC this way. It did not blank even after a few hours of idle time. So it probably only blanks when running on battery.

I was looking for a way around this, and I think I've finally got it!

Gnome Extension

I looked through the bug that was referenced here to find the link to that extension.

Check the current setting using:

gsettings get org.gnome.desktop.screensaver idle-activation-enabled

If the result is true turn it off using:

gsettings set org.gnome.desktop.screensaver idle-activation-enabled false

Second option to try is:

gsettings set org.gnome.settings-daemon.plugins.power idle-dim false

Gnome bug

There is a four year old Gnome bug addressing the issue of screen blanking immediately after lock here.