Comment # 6 on bug 1204864 from Fabian Vogt

(In reply to Andreas from comment #5)
> (In reply to Fabian Vogt from comment #4)
> > Display :99 sounds strange. Which display manager do you use? If it's
> > lightdm, try sddm or gdm.
> I'm using the default SDDM for KDE Plasma installation.

So the question is where DISPLAY=:99 is coming from. IIRC that's what Flatpak
sets inside the sandbox for X11 mediation. I have no idea what might send that
into the dbus activation environment.

> I reproduced this bug on Leap KDE Live CD
> 1. Install Firefox Flatpak
> 2. In the Firefox settings, set the opening of pdf files using the system
> application
> 3. Download pdf file and open
> 4. Relogin
> 5. Try to open it from downloads in Firefox

I have the suspicion that flatpak breaks this somehow. Can you try the
following (I don't have access to 15.4 myself currently):

1. qdbus-qt5 org.freedesktop.impl.portal.desktop.kde (to start the process
without using flatpak)
2. Relogin
3. Try to trigger the issue

And this:
1. Reproduce the issue
2. Run "qdbus-qt5 org.freedesktop.impl.portal.desktop.kde" (it should fail)
3. Run dbus-update-activation-environment --all
4. Try 2 again (it should succeed)
5. Try to trigger the issue again