[How To] make screen blank and lock?

[?XO]

I am back on my linux lite laptop, and want to run it 24/7, the issue i have is on windows i used to lock screen with (power button + L) which i was able to lock, as it was already in shortcuts. But another thing i was having on windows was pressing the power button only to turn off screen as it is always on, after pressing super + L screen goes black but i can still see screen backlight. i tried to make shortcut for making screen blank i was unable to use it with power button, and other keys were able to turn of screen when i was logged in not on lock screen. How can i do it?