Same Problem here again with Proxmox 5.4-3 without subscription, not being able to "apt update":
Ign:1 http://ftp.debian.org/debian stretch InRelease
Hit:2 http://ftp.debian.org/debian stretch Release
Hit:4 http://security.debian.org stretch/updates InRelease
Hit:5 http://download.proxmox.com/debian/pve stretch InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
W: Target Packages (pve-no-subscription/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Packages (pve-no-subscription/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Translations (pve-no-subscription/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Translations (pve-no-subscription/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Packages (pve-no-subscription/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Packages (pve-no-subscription/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Translations (pve-no-subscription/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Translations (pve-no-subscription/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
/etc/apt/sources.list:
deb http://ftp.debian.org/debian stretch main contrib
# PVE pve-no-subscription repository provided by proxmox.com,
# NOT recommended for production use
deb http://download.proxmox.com/debian/pve stretch pve-no-subscription
# security updates
deb http://security.debian.org stretch/updates main contrib
Ign:1 http://ftp.debian.org/debian stretch InRelease
Hit:2 http://ftp.debian.org/debian stretch Release
Hit:4 http://security.debian.org stretch/updates InRelease
Hit:5 http://download.proxmox.com/debian/pve stretch InRelease
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
W: Target Packages (pve-no-subscription/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Packages (pve-no-subscription/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Translations (pve-no-subscription/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Translations (pve-no-subscription/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Packages (pve-no-subscription/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Packages (pve-no-subscription/binary-all/Packages) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Translations (pve-no-subscription/i18n/Translation-en_US) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
W: Target Translations (pve-no-subscription/i18n/Translation-en) is configured multiple times in /etc/apt/sources.list:5 and /etc/apt/sources.list.d/pve-install-repo.list:1
/etc/apt/sources.list:
deb http://ftp.debian.org/debian stretch main contrib
# PVE pve-no-subscription repository provided by proxmox.com,
# NOT recommended for production use
deb http://download.proxmox.com/debian/pve stretch pve-no-subscription
# security updates
deb http://security.debian.org stretch/updates main contrib