I have an issue with mounting a cheap smart watch in #linux: Device is seen by the kernel, but never registered as a storage device /dev/sd*:

usb 1-2: new full-speed USB device number 3 using xhci_hcd
usb 1-2: New USB device found, idVendor=0e8d, idProduct=0002, bcdDevice= 1.00
...
usb-storage 1-2:1.0: USB Mass Storage device detected
scsi host0: usb-storage 1-2:1.0

@root42 I also had this problem once where the kernel showed the usb drive was plugged in but no /dev/sd* showed up, the problem was the usb kernel modules weren't loaded so 'modeprobe usb' or a similar modeprobe command to that fixed it