LUbuntu 20.04 LTS “Focal Fossa” comes with an integrated dark theme. You can activate the dark version of Ubuntu‘s default Yaru theme and get a dark GNOME desktop with just a few clicks. Here is how.
First, click the system menu button on the control panel in the upper right corner of the Ubuntu GNOME desktop and select Settings.
You can also click the “Show Applications” button in the lower left corner of your screen, search for the “Settings” application, and launch it from there.
In the Settings application, click the Appearance category.
By default, Ubuntu uses the “Standard” window color theme with dark toolbars and light content areas. To enable Ubuntu’s dark mode, click Dark instead.
To use a light mode without the dark toolbars, click Light instead.
Your change will take effect immediately. You can now close the window.
What’s new in Ubuntu 20.04 LTS “Focal Fossa”
Note that this does not change the Ubuntu panel interface to dark mode. To the examplewhen you click the menu button in the top right corner of your screen you will see that the background is light even when dark mode is on.
To change the panel theme, you need to install a GNOME shell extension. OMG! Ubuntu! has instructions that guide you through the installation process of the gnome-shell-extensions package, activate the “User Themes” extension and change the “Shell” theme to “Yaru-dark”.