held back packages

The following packages have been kept back:
  apache2 apache2-bin apache2-data apache2-utils build-essential curl
  default-jre default-jre-headless g++ gimp gimp-data gnome-orca
  gnome-themes-standard gobject-introspection grub-common grub-efi-amd64
  grub-efi-amd64-bin grub2-common imagemagick-6.q16 libffmpegthumbnailer4v5
  libgimp2.0 libgirepository-1.0-1 libgl1-mesa-dri libopenmpt0
  libpython3-stdlib libreoffice libreoffice-avmedia-backend-gstreamer
  libreoffice-base libreoffice-base-core libreoffice-base-drivers
  libreoffice-calc libreoffice-common libreoffice-core libreoffice-draw
  libreoffice-gtk3 libreoffice-help-en-us libreoffice-impress
  libreoffice-java-common libreoffice-math libreoffice-ogltrans
  libreoffice-pdfimport libreoffice-report-builder
  libreoffice-report-builder-bin libreoffice-script-provider-bsh
  libreoffice-script-provider-js libreoffice-script-provider-python
  libreoffice-sdbc-hsqldb libreoffice-sdbc-postgresql libreoffice-style-tango
  libreoffice-writer libstdc++6 libtbb2 lightdm-gtk-greeter mariadb-server
  nfs-common nfs-kernel-server python3 python3-apt python3-brlapi
  python3-cairo python3-cffi-backend python3-dbus python3-gi
  python3-markupsafe python3-minimal python3-parsedatetime
  python3-pkg-resources python3-pycurl python3-setuptools python3-uno
  python3-yaml python3-zope.hookable python3-zope.interface rpcbind
  task-desktop task-english task-mate-desktop task-ssh-server tasksel
  tasksel-data udiskie uno-libs3 ure xserver-xorg-core
  xserver-xorg-video-amdgpu xserver-xorg-video-ati xserver-xorg-video-fbdev
  xserver-xorg-video-intel xserver-xorg-video-nouveau xserver-xorg-video-qxl
  xserver-xorg-video-radeon xserver-xorg-video-vesa xserver-xorg-video-vmware
0 upgraded, 0 newly installed, 0 to remove and 93 not upgraded.