Ошибки при запуске `apt update`. W: NO PUB_KEY и пакет W:Target настроен несколько раз

Когда я пытаюсь обновить свою систему с помощью sudo apt-get update, я получаю следующее:

Hit:1 http://security.ubuntu.com/ubuntu focal-security InRelease
Hit:2 http://archive.ubuntu.com/ubuntu focal InRelease
Get:3 http://pkg.scaleft.com/deb linux InRelease [4808 B]
Hit:4 http://archive.ubuntu.com/ubuntu focal-updates InRelease
Hit:5 http://archive.ubuntu.com/ubuntu focal-backports InRelease
Err:3 http://pkg.scaleft.com/deb linux InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F716E939977FC428
Reading package lists... Done
W: GPG error: http://pkg.scaleft.com/deb linux InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F716E939977FC428
E: The repository 'http://pkg.scaleft.com/deb linux InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51
W: Target CNF (main/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51
W: Target CNF (main/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51

Как Могу ли я исправить это и обновить свою систему?

РЕДАКТИРОВАТЬ

Теперь я получаю:

root@PYAMMANO-68J9Z:/# echo "deb http://pkg.scaleft.com/deb linux main" | sudo tee -a /etc/apt/sources.list
deb http://pkg.scaleft.com/deb linux main
root@PYAMMANO-68J9Z:/# curl -fsSL https://dist.scaleft.com/pki/scaleft_deb_key.asc | gpg --dearmor | sudo tee /usr/share/keyrings/scaleft-archive-keyring.gpg > /dev/null
root@PYAMMANO-68J9Z:/# apt -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 95 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Setting up scaleft-server-tools (1.56.1) ...
System has not been booted with systemd as init system (PID 1). Can't operate.
Failed to connect to bus: Host is down
dpkg: error processing package scaleft-server-tools (--configure):
 installed scaleft-server-tools package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 scaleft-server-tools
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51
W: Target CNF (main/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51
W: Target CNF (main/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:51
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:52
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:52
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:52
W: Target CNF (main/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:52
W: Target CNF (main/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list:52
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list.d/scaleft.list:1
W: Target Packages (main/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list.d/scaleft.list:1
W: Target Translations (main/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list.d/scaleft.list:1
W: Target CNF (main/cnf/Commands-amd64) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list.d/scaleft.list:1
W: Target CNF (main/cnf/Commands-all) is configured multiple times in /etc/apt/sources.list:50 and /etc/apt/sources.list.d/scaleft.list:1
E: Sub-process /usr/bin/dpkg returned an error code (1)