Hi,
@timonych no-subscription is not available on HTTPS; only enterprises have HTTPS, so your config is wrong.
@ozgurce.ozturkce : you have a weird issue: the proxmox repository throws you an HTTP 400 error, like some sort of a filtering temper...
I have similliar poblem and I think the problem is that download.proxmox.com routes all http/https incoming traffic to enterprise.proxmox.com.
The portal asks username/password for access to download.proxmox.com via web or apt if I ignore ssl...