sudo chown www-data:www-data etc
sudo chmod 775 etc
sudo chown www-data:www-data /dev/usb/lp0
source:
https://www.howtogeek.com/169679/how-to-add-a-printer-to-your-raspberry-pi-or-other-linux-computer/
https://kernelmastery.com/enable-regular-users-to-add-printers-to-cups/
https://maker.pro/raspberry-pi/projects/how-to-turn-a-usb-printer-into-a-wireless-printer-with-raspberry-pi-zero-w