- alle VM´s beenden
2. Source.list verändern
nano /etc/apt/sources.list
# PVE pve-no-sub
deb http://download.proxmox.com/debian/pve bullseye pve-no-subscription
sollte dann so aussehen:

3. Danach alles auf Debian anpassen
sed -i 's/buster\/updates/bullseye-security/g;s/buster/bullseye/g' /etc/apt/sources.list
4. update + list-upgrade
apt update
apt dist-upgrade