Changing default file manager in Gnome3 (Fedora 22)
In Fedora 25, the appropriate file is /usr/share/applications/gnome-mimeapps.list
. Change the inode/directory
entry to point to your file manager of choice. Change takes place immediately and the Places menu opens the newly selected application.
You could try editing /usr/share/applications/defaults.list
and changing the line
inode/directory=nemo.desktop;caja.desktop;nautilus.desktop;Thunar.desktop;kde4-dolphin.desktop
to
inode/directory=Thunar.desktop;
or some order that suits your needs.