flatpak install flathub com.github.tchx84.Flatseal
5. Apply GTK system themes to Flatpak applications
You might have already noticed that most Flatpak apps don’t change their appearance as per the current system theme.
Why? Because Flatpak apps run inside a ‘container’ and don’t have access to the host filesystem, network, or physical devices.
You can choose to install themes as Flatpak to solve this issue. However, your favorite theme might not be available in Flatpak format.
Alternatively, you can make some manual effort and force the Flatpak applications to use a given theme. Here’s how to do that.
Step 1: Give Flatpak access to the folder where theme files are kept:
sudo flatpak override --filesystem=$HOME/.themes
Step 2: List all the themes available in ~/.themes location and then provide the folder name of the selected theme to Flatpak:
sudo flatpak override --env=GTK_THEME=chosen-theme
If you change the system theme later, you can change the theme for Flatpak in the same manner.
You can revert the changes using this command:
sudo flatpak override --reset
Read more about applying GTK theme to Flatpak apps in this article.
6. Update Flatpak apps and clean them
This is more for Flatpak unfriendly distributions like Ubuntu. If your distro doesn’t come baked in with Flatpak and you don’t have it integrated with the Software center, your installed Flatpak apps won’t be updated with system updates.
You can update all your installed Flatpak apps simultaneously with:
flatpak update