This is the official Opendesktop App. It allows you to directly install and apply most themes and other items for various DEs from within the app. Currently supported are Qt or GTK-based desktop environments.
More info Opendesktop
# Install the Opendektop App
Download the package for your Linux Distro under the Files tab.
Install the package with your package manager of choice, which should pull in any dependecies.
Or manually install the package by using the terminal:
The Opendesktop AppImages --install is optional, but recommended the install to enable the app self-updating feature and desktop menu registration. And you can uninstall the installed Opendesktop App AppImage by --uninstall option.