Just confirming, these are Workspace Reports? Or are they Legacy Reports, Report Builder Reports or Data Warehouse exports?
At this time, I don't believe that Workspace Reports can be sent to FTP
Legacy Reports can be, but it doesn't seem like a good idea to build out and schedule new reports for a feature that will soon be sunset... however, if you really need that I don;t know if that is still available? I don't see the option either....
Report Builder should have the option nested under the advanced options:
News > Advanced Delivery Options
File Options tab
FTP is an option here
Data Warehouse the FTP options are available under Advanced Delivery Options:
With the exception of the Legacy Reports (since they are being sunset), we can hope that FTP for Workspace Reports is on its way....