Hey there,
i have a Post from 2016 where i describe how to remove the Subscription popup in Proxmox. Since then there have been many changes to Proxmox and its not working since Proxmox 5 anymore.
But a great GitHub user named “Scott B” stepped in and published a nice tool to help users to remove the popup.
Here is the project and an install tutorial: https://github.com/foundObjects/pve-nag-buster
But dont forget if you like and use Proxmox a lot or event commercial! Please support the Proxmox team by buying a subscription if it’s within your means. High quality open source software like Proxmox needs our support!