aws-cli will sync your s3 buckets to a local system.

I’m doing that to linux, and then the Linux box is furthermore backed up with nakivo.

Not my favorite but the price was okay and I can run the whole director on Linux, unlike all their other competitors. [veeam’s next major release 13 or 14 should do this in the next year or so too.]

While nakivo backs up s3 buckets, NFS shares, and local file servers… to your point, I don’t trust it (or any other backup software I can’t extract and unpack the resulting backup by hand) as far as I can throw it. So I rsync or mirror it to a local Linux box with aws-cli and then back THAT up.

I think you can do all this with windows stuff too but I don’t know it that well

Additionally you can take servers that are linux vps’es and do the reverse: mirror THEIR content to an s3 bucket.

You can also run minio open source/free on your fileserver and set up s3 to s3 sync. Cloudflare for example will ingest and replicate your minio server automatically and you can firewall it all off to their address ranges. It’s not free but it actually prices out favorably compared to veeam and nakivo if that’s all you need backed up.