Solving: insufficient permissions for device: user in plugdev group; are your udev rules wrong

This happens on Ubuntu almost each time I add a new device:

Check that your are in plugdev group

$ id

uid=1000(alex) gid=1000(alex) groups=1000(alex),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),116(lpadmin),126(sambashare),127(kvm),129(libvirt),134(chrome-remote-desktop)

If not (i.e. plugdev not displayed), add it:

$ sudo usermod -aG plugdev alex

If you get 'insufficient permissions for device: user in plugdev group; are your udev rules wrong' when trying to debug, you'll need to add your device:

First i used lsusb to find my vendor id (here I guess google)

$ lsusb
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
...
Bus 001 Device 025: ID 18d1:4ee7 Google Inc.
..
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
..

Bus 001 Device 020: ID 05e0:2106 Symbol Technologies USB2.1 Hub

As suggested in https://developer.android.com/studio/run/device.html the solution was to

sudo gedit /etc/udev/rules.d/51-android.rules

Add the following

# Nokia 6.1
SUBSYSTEM=="usb", ATTR{idVendor}=="0489", MODE="0666", GROUP="plugdev"
# Asus Mi2 Lite
SUBSYSTEM=="usb", ATTR{idVendor}=="18d1", MODE="0666", GROUP="plugdev"

# Zebra

SUBSYSTEM=="usb", ATTR{idVendor}=="05e0", MODE="0666", GROUP="plugdev"

I simply did:

$ sudo chmod a+r /etc/udev/rules.d/51-android.rules
$ adb kill-server
$ adb devices
List of devices attached
00d60721d971c304