I think the solution should be to change x-www-browser to kfmclient openURL on Kubuntu.
This is certainly not a thunderbird bug, I think it's a kubuntu-default- settings bug. -- Kubuntu setting default components don't affect gnome/gtk apps https://launchpad.net/bugs/52670 -- kubuntu-bugs mailing list kubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/kubuntu-bugs
