Calibre is not a Client of Server. Calibre-companion WAS a good client until the current owners could not keep up with Android/iOs changes
(save your $ )
also,
https://manual.calibre-ebook.com/faq...rked-drive-nas, that should only be a COPY of the Library folder.
To interact with a 'Server' instance, just use your web browser Firefox, Edge... with that URL