Turning off screen in Linux

[Linux for blind general discussion]

And since Tim mentioned phones, I recently put a cheap smartphone on a
line no one in my household is using to try and learn Talkback, and
the plan is to keep the screen as dim as possible(ideally, I'd have it
completely dark and acting solely as a touchpad, though I have my
doubts there's a 0 brightness/touch-only setting for the screen.