Once upon a time Macrium indicated they did not yet have an ETA for backups to FTP. 
I'd like to see this for two reasons:
First, ransomware protection.  If backups are stored on an FTP server with a usercode/password not known to windows, that seriously reduces the chances that a ransomware attack will find them.  FTP good, Secure FTP even better.
Second, I've found my particular NAS has better FTP performance than CIFS.

Hello FloridaMatt,

Thanks for posting.

There isn't an official ETA for backups to FTP. There is a feature request open and I have updated it with your feedback.

Kind Regards

Stephen

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In the meantime, I use an application called Allway Sync that's inexpensive, actually free if your 30-day activity average stays below whatever it defines as casual use.  Its main purpose is to handle data replication, including multi-way sync (e.g. "Find the newest version of this file among these 4 locations and replicate it to the other 3").  I use it primarily for one-way synchronization from my laptop to various external hard drives for certain data, but it also supports FTP, WebDAV, lots of cloud storage providers through their native APIs, etc., and it can be configured to run in the background to execute on a schedule or when changes are detected, although when you run it manually you can run a pre-sync analysis to see visually exactly which files will be updated, deleted, added etc and even override the default actions on a per-file/folder basis if you for example want to bring back an old version of one file, prevent one from replicating this particular time, etc.  So yes it would be a two-step process until Reflect has native support for FTP, and might cost you a small amount, but it would achieve what you're looking for and you might find other uses for that application.