"Yes, rsync.net does support zfs send and receive, they have a special discount for that"

Yes, we do support zfs send/recv and it works just like you'd expect it to. We even have transfer resumes, etc., and we run the latest stable/production ZoL code for these accounts.

There is no discount for this. The price is the same as standard pricing but with a higher, 4TB minimum account size.

We have to give you a virtual machine and IP address, etc., which is why there is a higher minimum. If you have less than 4TB of assets to protect I would recommend using the excellent borg tool and a normal rsync.net account.

Here's the page: https://www.rsync.net/products/zfsintro.html , but it doesn't seem like there's a discount any more (probably because the regular price has dropped)

It's not a discount. It's a special account that forces you to have 4TB minimum which used to be 1TB, so it's not cheap just to have a small amount of data. In that case, better to just spin up your $5 instance and put zfs on it.