Fixed Broken Falkon DevTools on Nobara Linux (QtWebEngine Issue)

Fixed Broken Falkon DevTools on Nobara Linux

Today I ran into a strange issue with Falkon on Nobara Linux where:

• DevTools were broken / blank
• Inspector would not open properly
• Terminal showed:

Fontconfig error: Cannot load default config file: No such file: (null)

At first, it looked like a fontconfig problem, but after deep debugging it turned out to be a missing Qt WebEngine DevTools resource package.

What I Checked

Initially verified that Fontconfig was healthy:

fc-match sans
fc-conflist | head
ls /etc/fonts/fonts.conf

Everything worked correctly.

Also tested:

• clean XDG config
• disabling GPU
• forcing X11
• clearing caches
• checking environment variables

None fixed DevTools.

Real Root Cause

The actual issue was that the package:

qt6-qtwebengine-devtools

was NOT installed.

This package provides:

qtwebengine_devtools_resources.pak

which Chromium/QtWebEngine-based DevTools require internally.

Without it:

• Falkon DevTools break
• Inspector UI may be blank
• Developer console may fail entirely

How I Diagnosed It

Checked whether the devtools resource existed:

rpm -ql qt6-qtwebengine | grep devtools

Nothing appeared.

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Then searched providers:

sudo dnf provides '*qtwebengine_devtools_resources.pak*'

This revealed:

qt6-qtwebengine-devtools

Fix

Install the missing package:

sudo dnf install qt6-qtwebengine-devtools

Then verify:

ls /usr/share/qt6/resources/qtwebengine_devtools_resources.pak

Restart Falkon.

DevTools immediately started working again.

Important Note

The misleading part was the startup warning on opening devtools:

Fontconfig error: Cannot load default config file: No such file: (null)

In my case this turned out to be unrelated QtWebEngine noise rather than an actual broken fontconfig setup.

Affected Stack

Potentially relevant systems:

• KDE Plasma
• Qt6
• QtWebEngine
• Falkon
• Fedora/Nobara
• Wayland

Useful Commands Summary

Check if DevTools resources exist

find /usr -iname '*devtools*resources*'

Search which package provides them

sudo dnf provides '*qtwebengine_devtools_resources.pak*'

Install fix

sudo dnf install qt6-qtwebengine-devtools

Hopefully this saves someone several hours of debugging random fontconfig warnings that are actually hiding a missing QtWebEngine DevTools package.