Cardboard works quite well, but after a year it decomposes since the ground won't have grown over yet.
Honestly, passersby don't care 99% of the time what you do in your garden. A loose interruption of the sight lines is enough.
No one looks through a thick leafless hazelnut bush who is just passing by. Voyeurs are a different matter, and a privet won't stop them either.
Hazelnut is indestructible. Whether wet, dry, cold, or hot.
Elderberry is ecologically very valuable.
Don't ask who I've already startled. Smokers hang around the garden wall and don't even notice you're there, or waiting people stare absentmindedly into your garden. I have a parking lot on one property boundary and in front of the house the main road with a marketplace.
95% wouldn't even notice if you were working naked in your garden.