Download the file then move it and make executable and restart nautilus to see the Copy Path icon
wget https://gist.githubusercontent.com/meramsey/f1d20da371de82e801df19c92a673e63/raw/2bb9cb9007f21e85b00aade70d5db21c41b44f44/nautilus-copy-paths.py
sudo mv nautilus-copy-paths.py /usr/share/nautilus-python/extensions/nautilus-copy-paths.py
sudo chmod +x /usr/share/nautilus-python/extensions/nautilus-copy-paths.py
nautilus -q