Warning: The following solution should be used ONLY for iPod nano 6th generation.
The gtkpod homepage says the following :
6th generation iPod nano CANNOT be recorded unless a binary binary is used
The binary file (originally written for Ubuntu 12.04) can be downloaded and extracted from here or here, and it should work on Ubuntu (I tested it on Ubuntu 18.04) and Slackware.
You can find out if your system is 64-bit or 32-bit using the uname -i command. It will return i386 for 32-bit and x86_64 for 64-bit.
Unzip the archive.
Read readme.md.
For 64-bit Ubuntu, run:
sudo ./install_64bit.sh
For 32-bit Ubuntu, run:
sudo ./install_32bit.sh
After that, libgpod-based software such as gtkpod, Banshee, Rhythmbox, Amarok, Clementine (and its new fork of Strawberry), gPodder and some others should work with iPod nano 6th gen.
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