Here is a twist on this old thread. I just moved my Library from an old Windows 10 machine to the an Ubuntu 18.04 box.
Tarballed (yes tarballed using cygwin tools --
www.cygwin.com ) the configuration directory on the windows machine.
Copied to the new box -- installed Calibre for linux. Pointed it to the folder that I already copied my Library into during the initial wizard. shut down the calibre.
renamed the
/home/<user>/.config/calibre to
/home/<user>/.config/calibre.vanilla
untarred my old windows calibre folder in its place.
modified the global.py in the following ways:
my home folder is: /home/nrapopor change it to yours instead
database_path = '/home/nrapopor/library1.db'
library_path = u'/home/nrapopor/Calibre'
All my settings look good and all my plugins seem to work (so far) ...