Bug 509817

Summary:	Flatpak-installed GTK3 apps ignore Breeze theme and use Adwaita
Product:	[I don't know] kde	Reporter:	Luka Rasputin <nanoblade9>
Component:	general	Assignee:	Unassigned bugs <unassigned-bugs-null>
Status:	RESOLVED WORKSFORME
Severity:	minor	CC:	sitter
Priority:	NOR
Version First Reported In:	unspecified
Target Milestone:	---
Platform:	Arch Linux
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:
Attachments:	Screenshot of Lutris using Adwaita theme What Lutris should look like

Description Luka Rasputin 2025-09-23 07:42:39 UTC

SUMMARY
When I install a GTK3 application via Flatpak (for example, Lutris or GNOME Boxes), the application ignores the GTK3 theme configured in KDE System Settings (Breeze by default) and instead uses Adwaita.

This issue only happens under KDE Plasma. The same Flatpak apps respect the configured GTK3 theme when running under other desktop environments such as GNOME and Xfce.


STEPS TO REPRODUCE
1. Open KDE Plasma desktop (default settings, Breeze theme selected).
2. Install a GTK3 app via Flatpak, e.g.: flatpak install flathub net.lutris.Lutris
3. Launch the application.
4. Observe the application’s theme.

OBSERVED RESULT
The application uses Adwaita theme instead of Breeze.

EXPECTED RESULT
The application should respect the GTK3 theme configured in KDE System Settings (Breeze).

SOFTWARE/OS VERSIONS
KDE Plasma Version: 6.4.5
KDE Frameworks Version: 6.18.0
Qt Version: 6.9.2

ADDITIONAL INFORMATION
I’m aware that Flatpak uses sandboxing, which affects how theming works. However, I noticed that the Breeze theme is installed as a Flatpak dependency, yet GTK3 apps still don't use it.

Comment 1 Harald Sitter 2025-09-23 08:35:19 UTC

Works fine for me. Could you post a screenshot?

Comment 2 Luka Rasputin 2025-09-23 09:33:26 UTC

Created attachment 185182 [details]
Screenshot of Lutris using Adwaita theme

Comment 3 Harald Sitter 2025-09-23 10:34:38 UTC

Which items would you expect to look different?

Comment 4 Luka Rasputin 2025-09-23 11:03:49 UTC

Colors, icons and buttons in the header bar look different. Minimize and maximize buttons are missing.

Comment 5 Luka Rasputin 2025-09-23 11:04:39 UTC

Created attachment 185184 [details]
What Lutris should look like

Comment 6 Harald Sitter 2025-09-23 11:18:53 UTC

Yeah. Works fine for me. Can you reproduce this on a new installation and/or user?

Comment 7 Luka Rasputin 2025-09-23 14:03:28 UTC

(In reply to Harald Sitter from comment #6)
> Yeah. Works fine for me. Can you reproduce this on a new installation and/or
> user?

Yes, I can reproduce this on a fresh user account with default settings.

Comment 8 Luka Rasputin 2025-09-24 09:42:04 UTC

I'm not sure if it's related to this issue, but I noticed that plasma-xdg-desktop-portal-kde.service is not running.

[user@hostname ~]$ systemctl status --user plasma-xdg-desktop-portal-kde.service
○ plasma-xdg-desktop-portal-kde.service - Xdg Desktop Portal For KDE
     Loaded: loaded (/usr/lib/systemd/user/plasma-xdg-desktop-portal-kde.service; static)
     Active: inactive (dead)

Sep 24 12:08:37 hostname systemd[778]: Starting Xdg Desktop Portal For KDE...
Sep 24 12:08:37 hostname systemd[778]: Started Xdg Desktop Portal For KDE.
Sep 24 12:08:48 hostname xdg-desktop-portal-kde[1152]: qt.dbus.integration: QDBusConnection: couldn't handle call to CreateMonitor, no slot matched
Sep 24 12:08:48 hostname xdg-desktop-portal-kde[1152]: qt.dbus.integration: QDBusConnection: couldn't handle call to CreateMonitor, no slot matched
Sep 24 12:08:48 hostname xdg-desktop-portal-kde[1152]: qt.dbus.integration: Could not find slot InhibitPortal::CreateMonitor
Sep 24 12:09:39 hostname systemd[778]: Stopping Xdg Desktop Portal For KDE...
Sep 24 12:09:39 hostname systemd[778]: Stopped Xdg Desktop Portal For KDE.

Comment 9 Luka Rasputin 2025-09-27 16:11:33 UTC

Unfortunately, I don't know what causes this issue or how to reproduce it. Since I'm not using KDE anymore, I'm closing this.