Proxmox Community Updates

First remove the enterprise enterprise.proxmox repository

rm /etc/apt/sources.list.d/pve.enterprise

#apt update && apt -y full-upgrade

Add the no-subscription or pve-test repositori :

#nano /etc/apt/sources.list
deb http://download.proxmox.com/debian buster pve-no-subscription

Go back to the GUI and check you can get updates!