Get network interfaces on Linux
That is a huge docstring, it's longer than the code itself. You should read Python's PEP about how to write good docstrings.

For a start a docstring shouldn't contain examples, you can put that as a  regular comment in the script if you want. And you don't need to be so detailed and explicit about the type and optional nature of your parameters. I would take some information out of your parameters and returns sections and just fold it back into your opening section. Docstrings should be relatively concise and mostly add context and explanation.

A user can easily see the default parameters get_interfaces(external=False, ip=False), which reveals that they're optional and booleans. All you need to explain is what setting them will affect.