This annoys me a lot, as whenever I lock the screen, my big screen turns off and it is an old slow screen that takes a few seconds to turn on again.
To disable this behavior, do the following:
- Download this extension: https://www.dropbox.com/s/5owr2bxhbijdino/no-screen-blank%40example.com.zip?dl=1
- Extract the file and edit the metadata.json file, adding “3.28” to the list of supported shell-version
- Place the folder inside ~/.local/share/gnome-shell/extensions/
- Open gnome-tweaks (install it first by apt install gnome-tweaks if you don’t have it already)
- Go to Extensions and turn “No screen blank” extension on.
Note: I have uploaded the modified version to support Gnome 3.28 here.
Tested on Ubuntu 18.04 with Gnome 3.28.
Thanks go to the anonymous developer here, who did quite a good job!