The plugin is Fanficfare. I want to get the 4.19 version working so I can use FanFictionDownloader for browser cache for FF.net again,
since that's not possible anymore as of 4.20. I tried just replacing the fanfiction.net adapter file from the 4.19 version but that didn't work. :/
I guess if I can't get the duplicate plugin to work, I could install another instance of calibre and use the old version there, but I thought this would be easier 😂 Or I could just straight up go back to that version and only update the adapters I use, it's not that outdated (for now).