HOW TO: Apply Custom GTK Themes to Flatpaks

This is a short and sweet tutorial on how to apply custom GTK themes to your flatpaks.

By design flatpaks are limited in what they can access. However there’s an easy way to apply a custom theme to your flatpaks.

NOTE: In order to apply a custom theme to your flatpaks, the theme must be located in your ~/.themes folder.

HOW TO:

For this tutorial I’m going to use Bottles as an example which, by default, looks like this:

So let’s see how to apply my custom theme to Bottles:

1. Open a Terminal and run sudo flatpak override --filesystem=$HOME/.themes to give flatpak access to your themes folder

2. Now that flatpak has access to your themes folder, choose the theme you want to apply to flatpaks by running sudo flatpak override --env=GTK_THEME=theme-name.

NOTE: replace theme-name with the name of the theme you want to apply. In my case is WhiteSur-dark

3. You’re done. Now Bottles looks like this:

If you want to reverse the changes, open up a terminal and run sudo flatpak override --reset