Files lens and xdg-open only open nautilus but not the correct applicatiion

I had the same problem when I installed xfce (my question can be found here).

My problem was solved after uninstalling all xubuntu*, xfdesktop4* and xfce4* packages (and thunar).

Perhaps you should start by typing:

aptitude search xfce xfd xubuntu | grep ^i

in order to see which packages are installed in your system.

Then proceed with their uninstallation.

I had the same issue with the files-lens as well as in Chrome browser. I removed all xfce4 related packages and it fixed the issue. Thanks!

This is what I did,

sudo aptitude purge xfce4 desktop-base exo-utils gtk2-engines-xfce libexo-1-0 libexo-common libgarcon-1-0 libgarcon-common libthunarx-2-0 libtumbler-1-0 libxfce4ui-1-0 libxfce4util-bin libxfce4util-common libxfce4util4 libxfconf-0-2 orage tango-icon-theme thunar thunar-data thunar-volman tumbler tumbler-common xfce-keyboard-shortcuts xfce4 xfce4-appfinder xfce4-mixer xfce4-panel xfce4-session xfce4-settings xfce4-utils xfconf xfdesktop4 xfdesktop4-data xfwm4 xfwm4-themes

I found this information here