Install gnome-shell-extension-caffeine by entering the following commands in the terminal:
sudo apt update sudo apt install gnome-shell-extension-caffeine
Description:
GNOME Shell extension to keep your computer awake
This GNOME Shell extension provides an icon which can be toggled to inhibit the actions that would normally be taken when the system is idle, including screen locking, screensaver and automatic suspend. By default it also inhibits idle actions while any window is full-screen, and it can be configured to inhibit idle actions while user-specified applications have any window open. . Please note that each user will need to enable the extension manually, for example using the gnome-tweaks application.
Homepage: https://github.com/eonpatapon/gnome-shell-extension-caffeine
Version: 0~git20171229-2
Section: universe/gnome