Disabling the audio should be as simple as unplugging your earbuds from the 3.5mm jack

When you need to hear something or use a microphone, you plug the earbuds back in

The fact that there's nothing like this, no modern equivalent to the original ipod touch, really shows how dedicated to spying on us the whole tech industry is - they won't even let us have devices that can be used to avoid spying, they force you to have a camera and/or microphone and/or speakers in order to have a usable wifi device