Currently one can create remote backup storage using SMB/CIFS or NFS. Both protocols are not really suitable for offsite backups over the internet.
On the other hand, SSH (SFTP) is quite suitable for that process.
ISPs (like Hetzner) provide a cheap “storage box” product, which would work quite well in such a case. It also supports the borg backup protocol, which would be even better, supporting client side encryption of the backup data.