/Applications/calibre.app/Contents/MacOS/calibre --ignore-plugins
gives:
CALIBRE_CONFIG_DIRECTORY=/tmp/cal /Applications/calibre.app/Contents/MacOS/calibre-debug -g
does open Calibre, though obviously without the configuration changes I've made. So what do I do next? (This is where I'm hoping you give me a magic key to fix my own installation/configuration!)
Thank you so much for all your help so far, by the way.