Hello,
Since some time i've been using a maxtor 1tb usb hard drive and I had no issues. I was a bit short on storage space and I bought 2 usb hard drives (2.5") of 5tb each:
Backup Plus Portable 5 TB Black
STHP5000400
backup-plus-portable-apac-ds2004-4-1904-apac-en_as.pdf
When i connect the hard drive, it can sometimes automount but it takes ages, then it's super slow (no issues detected when using on my computer). the seagate came formatted in exfat and i changed it into ntsf.
When I select add a new source, the hard drives doesn't shows up. I add to click on NETWORK FILE SYSTEM, then the hard drive will show up. When I connect my MAXTOR drive I don't have to do that nor I do have select anything, it's there from the start (when plugged) even after formating the SD card where I boot LIBRELEC.
Any help advised 
PS: I formated the sd card and installed OSMC just to see what would happen. It detects my USB hard drives normally. Got an EFI partition showing though...(no idea why). Thing is the scrapper really missmatch lots of tv shows names
