sudo apt install systemd=229-4ubuntu4
[sudo] password for edoardo:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 systemd : Depends: libsystemd0 (= 229-4ubuntu4) but 229-4ubuntu21.10 is to be installed
           Recommends: libpam-systemd but it is not going to be installed
E: Unable to correct problems, you have held broken packages.



sudo apt install systemd=229-4ubuntu4 libsystemd0=229-4ubuntu4
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  app-install-data appstream-data-pantheon-loki-stable appstream-data-pantheon-loki-stable-icons cdparanoia cdrdao cerbere chmsee cinnamon-desktop-data cinnamon-l10n
  colord-data dns-root-data dnsmasq-base elementary-keyring fieldworks-enc-converters fonts-ancient-scripts fonts-sil-ezra fonts-sil-galatia fuseiso fuseiso9660 gdisk
  grub-pc-bin gtk-sharp2-sil gvfs-libs hplip-data hwinfo iputils-arping k3b-data libasyncns0:i386 libatasmart4 libcinnamon-desktop4 libcolorhug2 libflac8:i386 libgail-3-0
  libgdiplus libgdiplus-sil libglu1-mesa:i386 libhd21 libhunspell-dev libjson-c2:i386 libk3b6 libk3b6-extracodecs libkcddb4 libkcompactdisc4 libmono-accessibility4.0-cil
  libmono-data-tds4.0-cil libmono-ldap4.0-cil libmono-messaging4.0-cil libmono-relaxng4.0-cil libmono-sqlite4.0-cil libmono-system-componentmodel-composition4.0-cil
  libmono-system-componentmodel-dataannotations4.0-cil libmono-system-configuration-install4.0-cil libmono-system-data4.0-cil libmono-system-design4.0-cil
  libmono-system-drawing4.0-cil libmono-system-enterpriseservices4.0-cil libmono-system-identitymodel-selectors4.0-cil libmono-system-identitymodel4.0-cil
  libmono-system-ldap4.0-cil libmono-system-messaging4.0-cil libmono-system-numerics4.0-cil libmono-system-runtime-serialization-formatters-soap4.0-cil
  libmono-system-runtime-serialization4.0-cil libmono-system-servicemodel-activation4.0-cil libmono-system-servicemodel-internals0.0-cil libmono-system-servicemodel4.0a-cil
  libmono-system-serviceprocess4.0-cil libmono-system-transactions4.0-cil libmono-system-web-applicationservices4.0-cil libmono-system-web-services4.0-cil
  libmono-system-web4.0-cil libmono-system-windows-forms4.0-cil libmono-system-xml-linq4.0-cil libmono-webbrowser4.0-cil libmusicbrainz5cc2v5 libndp0 libnemo-extension1
  libnetfilter-conntrack3 libogg0:i386 libpantheon-files-core0 libpantheon-files-widgets0 libperl4-corelibs-perl libpolkit-backend-1-0 libsane-hpaio libsilcc0
  libsndfile1:i386 libvorbis0a:i386 libvorbisenc2:i386 libwebrtc-audio-processing-0 libwrap0:i386 libx86emu1 libxcursor1:i386 mono-basic-sil mono-sil nemo-data
  notify-osd-icons pso-keys python3-pexpect python3-pil python3-ptyprocess python3-renderpm python3-reportlab python3-reportlab-accel rtkit ttf-ancient-fonts vcdimager
Use 'sudo apt autoremove' to remove them.
Suggested packages:
  systemd-ui systemd-container
Recommended packages:
  libpam-systemd
The following packages will be REMOVED
  appcenter aptdaemon capnet-assist colord crossover:i386 deja-dup-backend-gvfs elementary-standard elementary-tweaks fieldworks fieldworks-applications flexbridge
  furiusisomount gala gnome-disk-utility gnome-settings-daemon grub-customizer gvfs gvfs-backends gvfs-daemons gvfs-fuse hplip indicator-brightness k3b
  libavahi-client3:i386 libcanberra-pulse libcups2:i386 libdbus-1-3:i386 libpam-systemd libpulse0:i386 libsystemd0:i386 nautilus nemo nemo-fileroller network-manager
  network-manager-gnome packagekit packagekit-tools pantheon-files pantheon-shell pantheon-xsession-settings policykit-1 policykit-1-gnome printer-driver-postscript-hp
  pulseaudio pulseaudio-module-x11 sessioninstaller switchboard-plug-notifications switchboard-plug-pantheon-shell system-config-printer-gnome tlp-rdw ubuntu-system-service
  udisks2 woeusb
The following packages will be DOWNGRADED:
  libsystemd0 systemd
0 to upgrade, 0 to newly install, 2 to downgrade, 53 to remove and 2 not to upgrade.
Need to get 3.852 kB of archives.
After this operation, 1.015 MB disk space will be freed.
Do you want to continue? [Y/n] n