In 2009 there were few plug-ins. In 2019, there are many. See:
http://plugins.calibre-ebook.com/ for the official list of plug-ins that is updated by Calibre itself every time that a plug-in is updated. The Mobileread.com plug-in index has stale information because it is not automatically updated as
http://plugins.calibre-ebook.com/ is.
DaltonST