How to change "Global Dark Theme" on and off through Terminal?

To set the global dark theme from the command line, first navigate to a Terminal of your choice and then from within the shell emulator ...

Navigate to your home directory:

 cd ~

Create a new file called settings.ini inside of the GTK 4 directory:

 nano ~/.config/gtk-4.0/settings.ini

Enter the following fields into the configuration file:

[Settings]
gtk-application-prefer-dark-theme=1

Write the changes to disk by pressing control + x, then press y, then enter.

For modern Gnome desktops:

• Tested: Ubuntu 18.04, 20.04; Fedora 27, 32

Default dark mode:

gsettings set org.gnome.desktop.interface gtk-theme 'Adwaita-dark'

Default light mode:

gsettings set org.gnome.desktop.interface gtk-theme 'Adwaita'

Getting a list of available base theme names:

ls -d /usr/share/themes/* |xargs -L 1 basename

Caveats:

• Some existing limitations to changing the theme: https://bugzilla.gnome.org/show_bug.cgi?id=783666 (bug conversation mentions them)

• It appears that there's some variance in how this is adopted with Adwaita being the currently accepted default, but the tweak tool will also attempt to write to the settings.ini files.

• Furthemore, applications provided as snaps may ship with their own settings.ini files making a command line solution much more difficult than a one-liner.

Ideally, a technique to invoke gnome-tweak-tool through CLI would cover most scenarios holistically. Gnome-tweak-tool is written in python3, so this should be theoretically possible to someone familiar with Python.