PBS is a dedicated backup solution for VMs and LXC containers with incremental backups, block-level deduplication, and end-to-end encryption.
proxmox-backup-manager datastore create backup-store /mnt/backup
proxmox-backup-manager user create backup@pbs --password BackupPass123
proxmox-backup-manager acl update /datastore/backup-store --auth-id backup@pbs --role DatastoreBackup
Store the encryption key separately from PBS. Without it, restoring encrypted backups is impossible.