As a collector of epubs, 21.5k books now, and fixing all entries to todays standards e.g as correct as possible meta-data.
I am looking for a plugin that converts a selected ISBN to ISBN13 or a plugin that allows to sort/select all none-ISBN13.
Is there any work in progress that would help in that or does anyone now the trick to sort?
Conversion tools are available outside Calibre as
here:
https://www.boek.nl/content/nurcode