proxmox host

Hey everyone, I'm having some issues while trying to update my proxmox host, everytime I run sudo apt update from the cli (SSH) I get this error message. Err:1 http://download.proxmox.com/debian/pve bullseye InRelease...

I was wondering the other day... Since I do backups of all my VMs every night, what the best practice would be to backup the main files of the proxmox host itself. Let's say there's a fatal failure on a single node where the drives crash and one has to rebuild the proxmox host on new hardware...