Comment 2 for bug 1827975

dpkg: cycle found while processing triggers:
 chain of packages whose triggers are or may be responsible:
  man-db -> menu
 packages' pending triggers which are or may be unresolvable:
  man-db: /usr/share/man
  systemd: /etc/init.d
  doc-base: /usr/share/doc-base
  menu: /usr/share/menu

There's no real cycle here (while menu installs manual pages, man-db for its part doesn't install anything that would cause menu to be triggered), so I think this must be a dpkg bug.