Like so many things, it depends-

How quickly do you need to be able to restore? Is it commercial or homelab?

The most cost-effective option by far would be to put a NAS device someplace offsite. You could use tailscale to connect to it remotely.

After that, depending on your access patterns, either a glacier-style s3 service (aws or backblaze/etc), or a rented bare-metal server with big disks some place inexpensive.

This is for a "warm" backup as opposed to a hot backup so restoration timeline would be like seven days.