How to transfer between SD Card and External Hard drive using Samsung S8 and NO PC?

I am on S8 Exynos (Custom ROM - Renovate ICE, LATEST). When I was using a S7 last time and had a USB OTG cable to daisy chain my SD card reader and USB hard drive, the connection dropped so frequently that it made it impossible to transfer all my contents (around 120GB per day of photos and videos) from the SD card to my external hard drive. Is there a more reliable method using my S8? I also have the WD Wireless Pro, but it is giving me so many errors that I gave up on that device. I would like to reiterate that this is for travelling purposes, where I have to transfer nearly 200GB daily, and I hope not to lug my laptop around with me, hence asking whether my S8 can act as the intermediary.