echo "deb https://mirrors.tuna.tsinghua.edu.cn/proxmox/debian bullseye pve-no-subscription" > /etc/apt/sources.list.d/pve-no-subscription.list
rm /etc/apt/sources.list.d/pve-enterprise.list

apt update
apt upgrade
apt install -f
apt install pve-headers
dpkg-reconfigure pve-kernel-xxx
sed -i.bak 's|download.proxmox.com|mirrors.tuna.tsinghua.edu.cn/proxmox|g' /usr/share/perl5/PVE/APLInfo.pm
sed -Ezi.bak "s/(Ext.Msg.show\(\{\s+title: gettext\('No valid sub)/void\(\{ \/\/\1/g" /usr/share/javascript/proxmox-widget-toolkit/proxmoxlib.js && systemctl restart pveproxy.service
pveam update