I am using a Proxmox VE for a while. It is almost one month I start to use Proxmox VE 5.3-8.
I noticed that Proxmox VE has newer version released. Now it is v5.4-4.
I have not subscribe the license of PVE.
Here is a simple guide to show you how to upgrade Proxmox VE 5.3x to v5.4x
1) Edit /etc/apt/sources.list.d/pve-enterprise.list
Comment or delete the following line.
deb https://enterprise.proxmox.com/debian/pve stretch pve-enterprise
2) Edit /etc/apt/sources.list
Add following line at the end of the file.
deb http://download.proxmox.com/debian stretch pve-no-subscription
3) Now, it is OK to do the update.
After the upgrade