You are getting this error because the hci0 device could not be enabled on your host system, the echo command sends that to
the remote device using Bluetooth. You need a Bluetooth dongle plugged into your PC which supports Bluetooth 4.0+ (and must have support for Bluetooth Low Energy). You can use the
BlueZ commands to see what Bluetooth devices you have on your system and the corresponding LMP versions. You need a device with LMP version 6 or newer.
