I plugged in a D-Link DUB-1312 to my laptop running Ubuntu Zesty but Network Manager said that the interface was “not managed”.

The fix, found here, is to remove the contents of one file. Better to save the original file and touch an empty one:

$ sudo mv    /usr/lib/NetworkManager/conf.d/10-globally-managed-devices.conf{,_ORIGINAL}
$ sudo touch /usr/lib/NetworkManager/conf.d/10-globally-managed-devices.conf

For reference, here's the info about the DUB-1312 USB ethernet adapter:

<pre>$ sudo apt update
$ sudo apt install hwinfo
$ sudo hwinfo --netcard

(other output snipped)

40: USB 00.0: 0200 Ethernet controller
  [Created at usb.122]
  Unique ID: VQs5.d0KcpDt5qE6
  Parent ID: 75L1.MLPSY0FvjsF
  SysFS ID: /devices/pci0000:00/0000:00:14.0/usb2/2-6/2-6.4/2-6.4.3/2-6.4.3:1.0
  SysFS BusID: 2-6.4.3:1.0
  Hardware Class: network
  Model: "D-Link DUB-1312"
  Hotplug: USB
  Vendor: usb 0x2001 "D-Link"
  Device: usb 0x4a00 "D-Link DUB-1312"
  Revision: "1.00"
  Serial ID: "000000000005FA"
  Driver: "ax88179_178a"
  Driver Modules: "ax88179_178a"
  Device File: enxe46f13f4be18
  HW Address: e4:6f:13:f4:be:18
  Permanent HW Address: e4:6f:13:f4:be:18
  Link detected: yes
  Module Alias: "usb:v2001p4A00d0100dcFFdscFFdp00icFFiscFFip00in00"
  Driver Info #0:
    Driver Status: ax88179_178a is active
    Driver Activation Cmd: "modprobe ax88179_178a"
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #33 (Hub)