An automatic update has removed snapd from my system, I didn't want that. From the log file /var/log/apt/history.log :
Start-Date: 2020-11-04 20:20:39
Commandline: aptdaemon role='role-commit-packages' sender=':1.1560'
Install: libpam0g:i386 (1.3.1-5ubuntu4.1, automatic), libdevmapper1.02.1:i386 (2:1.02.167-1ubuntu1, automatic), libseccomp2:i386 (2.4.3-1ubuntu3.20.04.3, automatic), libargon2-1:i386 (0~20171227-0.2, automatic), libacl1:i386 (2.2.53-6, automatic), libkmod2:i386 (27-1ubuntu2, automatic), libapparmor1:i386 (2.13.3-7ubuntu5.1, automatic), systemd-timesyncd:i386 (245.4-4ubuntu3.3, automatic), systemd:i386 (245.4-4ubuntu3.3, automatic), libcap-ng0:i386 (0.7.9-2.1build1, automatic), libcryptsetup12:i386 (2:2.2.2-3ubuntu2.3, automatic), libjson-c4:i386 (0.13.1+dfsg-7ubuntu0.3, automatic), libip4tc2:i386 (1.8.4-3ubuntu2, automatic), libaudit1:i386 (1:2.8.5-2ubuntu6, automatic)
Upgrade: signal-desktop:amd64 (1.37.2, 1.37.3), libsystemd0:amd64 (245.4-4ubuntu3.2, 245.4-4ubuntu3.3), libsystemd0:i386 (245.4-4ubuntu3.2, 245.4-4ubuntu3.3), gir1.2-accountsservice-1.0:amd64 (0.6.55-0ubuntu12~20.04.2, 0.6.55-0ubuntu12~20.04.4), gdm3:amd64 (3.36.3-0ubuntu0.20.04.1, 3.36.3-0ubuntu0.20.04.2), gir1.2-gdm-1.0:amd64 (3.36.3-0ubuntu0.20.04.1, 3.36.3-0ubuntu0.20.04.2), libgdm1:amd64 (3.36.3-0ubuntu0.20.04.1, 3.36.3-0ubuntu0.20.04.2), python3-cryptography:amd64 (2.8-3, 2.8-3ubuntu0.1), libnss-myhostname:amd64 (245.4-4ubuntu3.2, 245.4-4ubuntu3.3), systemd-sysv:amd64 (245.4-4ubuntu3.2, 245.4-4ubuntu3.3), chromium-codecs-ffmpeg-extra:amd64 (1:85.0.4183.83-0ubuntu0.20.04.1, 1:85.0.4183.83-0ubuntu0.20.04.2), libpam-systemd:amd64 (245.4-4ubuntu3.2, 245.4-4ubuntu3.3), libnss-systemd:amd64 (245.4-4ubuntu3.2, 245.4-4ubuntu3.3), libnetplan0:amd64 (0.100-0ubuntu4~20.04.2, 0.100-0ubuntu4~20.04.3), spice-vdagent:amd64 (0.19.0-2, 0.19.0-2ubuntu0.2), accountsservice:amd64 (0.6.55-0ubuntu12~20.04.2, 0.6.55-0ubuntu12~20.04.4), libaccountsservice0:amd64 (0.6.55-0ubuntu12~20.04.2, 0.6.55-0ubuntu12~20.04.4)
Remove: netplan.io:amd64 (0.100-0ubuntu4~20.04.2), gnome-software-plugin-snap:amd64 (3.36.1-0ubuntu0.20.04.0), snapd:amd64 (2.47.1+20.04), plymouth-label:amd64 (0.9.4git20200323-0ubuntu6.1), plymouth-theme-ubuntu-text:amd64 (0.9.4git20200323-0ubuntu6.1), systemd-timesyncd:amd64 (245.4-4ubuntu3.2), nplan:amd64 (0.99-0ubuntu3~18.04.3), ubuntu-minimal:amd64 (1.450.2), plymouth-theme-spinner:amd64 (0.9.4git20200323-0ubuntu6.1), systemd:amd64 (245.4-4ubuntu3.2), plymouth:amd64 (0.9.4git20200323-0ubuntu6.1), dbus-user-session:amd64 (1.12.16-2ubuntu2.1), plymouth-theme-ubuntu-logo:amd64 (0.9.4git20200323-0ubuntu6.1)
ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: aptdaemon 1.1.1+bzr982-0ubuntu32.2
ProcVersionSignature: Ubuntu 5.4.0-52.57-generic 5.4.65
Uname: Linux 5.4.0-52-generic x86_64
NonfreeKernelModules: v4l2loopback_dc
ApportVersion: 2.20.11-0ubuntu27.11
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Fri Nov 6 09:44:08 2020
InstallationDate: Installed on 2018-05-04 (916 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
ProcEnviron:
TERM=xterm-256color
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=de_DE.UTF-8
SHELL=/usr/bin/zsh
SourcePackage: aptdaemon
UpgradeStatus: Upgraded to focal on 2020-09-30 (36 days ago)
Please note that this update has also replaced systemd:amd64 by systemd:i386 opening a can of worms.