For the Warnings:
Simply remove one of the duplicate entries of the: pve-no-subscription repository; either in: /etc/apt/sources.listor delete the: /etc/apt/sources.list.d/pve-no-subscription.list file, if it contains only that one repository.
For the Error:
You need to fix that third-party repository. It does not come from Proxmox and has nothing to do with it.
Is it this: [1]? If yes, not sure what you want with this ancient (Ubuntu) stuff directly on the PVE-host...