Prefer the old default Ambiance (or Radiance) app theme in Ubuntu 18.04? Well, it’s easy to install it in Ubuntu 20.04 and Ubuntu 20.10.
Ubuntu switched to Yaru themes since 19.10 Eoan. The old default Ambiance and Radiance (the light version) GTK themes are still available to install in Ubuntu via the light-themes package.
1. To install the GTK Theme:
Open terminal either by pressing Ctrl+Alt+T on keyboard, or by searching for ‘terminal’ from system application launcher.
When terminal opens, run command:
sudo apt install light-themes
2. To Apply the new theme in Ubuntu:
Now open Gnome Tweaks (install it from the Software app if you don’t have it) and go to Appearance in left pane.
Then you can select ‘Ambiance’ or ‘Radiance’ as theme of applications.
That’s it. Enjoy!