SUMMARY After installing Neon 5.27 and the Plasma Integration extension in Firefox 123.0 it could not connect to the native host. After some research I found that disabling AppArmor for Firefox fixes the issue. Article in question: https://discuss.kde.org/t/firefox-extension-plasma-integration/4583/7 STEPS TO REPRODUCE 1. Enable AppArmor for Firefox or have it enabled on installation. Commands to enable AppArmor: sudo rm /etc/apparmor.d/disable/usr.bin.firefox cat /etc/apparmor.d/usr.bin.firefox | sudo apparmor_parser 2. Plasma integration fails to connect to native host. 3. Disable AppArmor for Firefox. Commands to disable: sudo ln -s /etc/apparmor.d/usr.bin.firefox /etc/apparmor.d/disable/ sudo apparmor_parser -R /etc/apparmor.d/usr.bin.firefox 4. Plasma Integration works after restarting Firefox. OBSERVED RESULT Plasma Integration does not work with AppArmor enabled. EXPECTED RESULT Plasma Integration should work with AppArmor enabled for Firefox like it is on install. SOFTWARE/OS VERSIONS Linux/KDE Plasma: KDE Plasma Version: 5.27.10 KDE Frameworks Version: 5.114.0 Qt Version: 5.15.12
If AppArmor blocks access to the host, then that's AppArmor. Nothing we can do.
Tracked in bug 397399 already and a while ago I opened bug 475786 to have it backported to the KDE Neon AppArmor packages. *** This bug has been marked as a duplicate of bug 397399 ***