Binary package “libnotmuch5” in ubuntu bionic

thread-based email index, search and tagging (runtime)

 Notmuch is a system for indexing, searching, reading, and tagging
 large collections of email messages in maildir or mh format. It uses
 the Xapian library to provide fast, full-text search with a very
 convenient search syntax.
 .
 This package contains the runtime library, necessary to run
 applications using libnotmuch.