Comment 36 for bug 1551171

Are you going to fix this one day? The bug exists now over a decade, the internet is full of help requests and no one seems to care …

https://www.google.de/search?hl=de&source=hp&q=firefox%20kde%20okular%20pdf%20system%20handler&aq=f&aqi=g10&aql=&oq=&cad=h

Just use xdg-mime to make it cross desktop compatible. Gnome is just one fucking desktop on Linux, but its still the only one that is supported by Firefox.