One of my favorite things about running KDE’s own distro, KDE Neon, is how it defaults to using the KDE file UI in Firefox. I’m not sure why Kubuntu and Fedora KDE don’t know this, but it’s easy enough to configure.

Installation

The magic behind this is Firefox’s ability to use an XDG desktop portal. You probably already have the KDE XDG desktop portal installed, but if not, simply run:

Fedora

sudo dnf -y install xdg-desktop-portal-kde

Kubuntu

sudo apt install xdg-desktop-portal-kde

Configuring Your Shell

Next, we tell GTK apps, like Firefox, to use the KDE file dialogs if they’re able. We do that by setting in a variable in either our ZSH or BASH configuration (whichever your default shell is).

ZSH

echo export GTK_USE_PORTAL=1 >> .zprofile

BASH

echo export GTK_USE_PORTAL=1 >> .profile

Now just log out and back in and you get should native KDE file dialogs when saving or opening files with Firefox!