From your description, you appear to be using the USB HDD as a NAS (network attached storage) device.
You could look into buying a true NAS - i.e. a disk that is connected directly to the home network (either via wired or wireless connection), rather than via a USB port on the router.
Likely to be a faster, more versatile, but more expensive solution.
google "nas storage for ipad" for more information - e.g.
https://www.macworld.co.uk/feature/m...s-mac-3674321/
I think the connector you are referring to is a "Lightning" connector - Apple's (not cheap) Lightning to USB Camera Adapter - that allows a standard USB storage device to be connected to an ipad.
Possibly the Apple tech person was saying that the FileBrowser App has fairly recently extended support to use this for any file types, not just photos.
Also, the USB drive being connected has to have its own power source, as the Lightning adapter won't power it.
You could also look at one of these:
- not a recommendation, just an observation. Pricey, but if it gives you the interoperability you need quickly and easily, it might be worth a look.