From a non-expert, I have been pointed here by someone on the forum. FF has suddenly started opening nautilus instead of my preferred Dolphin. Dropbox is now doing this also. It is extremely annoying. My forum advisor suggested sudo update-mime-database /usr/share/mime/ But this has not cured it. Is the only option to uninstall nautilus? https://forums.opensuse.org/showthread.php/504039-Firefox-has-started-a-very-annoying-behaviour!?p=2687489#post2687489