What I have:
ClearOS 7 running as gateway on multihomed HP desktop. External IP xxx.xxx.xxx.xxx.
LAN1 = 192.168.1.1
LAN2 = 192.168.2.1

LAN1 has several Windows 11 computers connected to Netgear switch

What I want:
To be able to offer files stored on external USB hard drives connected to one of the Windows 11 computers on LAN1
AND to be able to select and retreive files stored on an external USB drive attached to a distant computer - outside of LAN... outside of local network.

Simply put, I want FTPS to operate through gateway.

I have WinSCP, IIS, PuTTy...

How to allow WinSCP to pass FTPS through gateway?

If not possible, do external drives have to be mounted onto gateway for Flexshare to work? If yes, please step-by-step. If no, please explain in depth.

OR please direct me to appropriate knowledge base (I've looked...) or forum topic (also looked...)