In later versions of Proxmox 8 you can manage your repositories from the GUI. If you’re getting the 401 Unauthorized, IP Not Allowed error, check the below.

Disable the Enterprise repositories and add the non-production Proxmox repository (read the warning)

Then click on Updates, Refresh, and it should all work.

promox repositories screen

Now you can install updates on your free tier Proxmox instance.