Setup Proxmox

Proxmox Documentation

https://www.proxmox.com/en/proxmox-virtual-environment/get-started

https://pve.proxmox.com/pve-docs/chapter-pve-installation.html

Enable No-Subscription Repository in web-GUI

node on the left -> Updates -> Repositories.
Disable the enterprise repository and add the No-Subscription repository
Go to the upper menu Update, press Refresh, then Upgrade

Untested Community Script

This script is quite popular in the homelab-community, but I never tried it. Look at the source code, if in doubt. No warranties at all.
https://community-scripts.github.io/ProxmoxVE/scripts?id=post-pve-install