A particular USB harddrive won’t show up in the device list under Ubuntu 18.04 when connected to a USB 3.0 port of the HP proliant microsever gen8 though it will show up when connected to a USB 2.0 port. The symptoms are that the drive won’t list with fdisk -l nor how up under /dev/sdX.
By chance I found that querying for USB devices in verbose mode gets the drive recognised by Linux:
lsusb -v
George's Techblog 