[nxbp]

What? It really couldn't be simpler: You open settings -> screensaver, choose blank after N minutes and close the settings window. Works.

[qot]

I have no screensaver options under settings: https://i.imgur.com/WM3xIWL.png

Note, I'm using Debian Sid. Gnome 3.36.2 on Wayland.

[nano9]

Try looking under Power.

[qot]

Nope, this is quite the opposite of black: https://i.imgur.com/L0O0fNn.png

It also turns my display off, which is not what I want: https://i.imgur.com/z5BIqGj.png

Seems like it's not as simple as @nxbp claims.