Emacs shortcut is convinent for text input. (Ctrl+F forward, Ctrl+B backward, etc.)
Input boxes on ubuntu does not use emacs shortcut. This command modify system defaults to use emacs keys.

gsettings set org.gnome.desktop.interface gtk-key-theme "Emacs"

To go back, use:

gsettings set org.gnome.desktop.interface gtk-key-theme "Default"