calibre is an e-book library manager. It can view,
convert and catalog ebooks in most of the major e-book formats.
It can also talk to a few e-book reader devices. It can go out
to the Internet and fetch metadata for your books.
It can download newspapers and convert them into e-books for convenient reading.

ATTENTION: Version 7.4.0 is the last one which can build under Leap because need Qt6 >= 6.5.3 to run.