ubuntu-defaults-builder binary package in Ubuntu Bionic amd64

 This tool allows you to create a "default settings" package for Ubuntu. The
 "ubuntu-defaults-template" script will generate a source package with the
 customizable settings (e. g. desktop/background.jpg and
 webbrowser/bookmarks-menu.txt). When built and installed, it will take the
 necessary actions to modify the system-wide defaults for desktops, programs,
 etc.
 .
 The main purpose for this is to provide a standard and safe way to create
 localized Ubuntu images, or OEM custom projects.
 .
 You can customize the following settings:
 .
  * Web browser start page, default search engine, and bookmarks (supports
    Firefox right now)
  * Unity/Unity 2D launchers
  * Desktop background (for GNOME right now)
  * Default desktop session in LightDM/gdm
  * Default radio stations in Rhythmbox and Banshee
  * Extra dependencies (Depends: and Recommends:), i. e. packages that are
    installed by default on the customized image
  * Internationalization (default locale, keyboard layout, language support)
    (only for built images, not configured by the defaults package itself)

Source package