SUMMARY opening web links on flatpak apps open up whatever I have associated on GNOME instead. so do "Show containing folder on file manager" actions - so I deleted nautilus, and now it tries to open Visual Studio Code ._. STEPS TO REPRODUCE 1. change default browser app in system settings 2. open a link in a flatpak'd app OBSERVED RESULT it will open either in whatever you had set in GNOME as default, if you uninstall it will open on some random app. I don't know what happens if you never had GNOME installed EXPECTED RESULT respecting defaults SOFTWARE/OS VERSIONS Linux/KDE Plasma: (available in About System) KDE Plasma Version: 5.22.4 KDE Frameworks Version: 5.83.0 Qt Version: 5.15.2 ADDITIONAL INFORMATION seems to happen to all flatpak apps, be it Qt GTK or Electron (GTK too)
AFAIK opening URLs via portals does not go through the portal backends. It is all handled in the xdg-desktop-portal frontend: https://github.com/flatpak/xdg-desktop-portal/blob/master/src/open-uri.c I think this is the same root cause as I am seeing for (non-Flatpak'd) Firefox where files are opened with other apps than expected. IIRC that's due to GTK and KDE having different interpretations/implementations of the mime type handling, but I don't remember the details well enough to judge who needs fixing
The case of opening URLs should be fixed with https://github.com/flatpak/xdg-desktop-portal/pull/473
*** This bug has been marked as a duplicate of bug 420050 ***