Simon, thank you for testing. Can you repeat the tests after running
lpadmin -p Lexmark_S300S400_Series -R usb-unidir
This removes the forced uni-directional mode. Lexmark's proprietary driver needs bi-directional communication.
Don't worry about firewall warnings, this is a bug in Lexmark's installer, it probably does not recognize that you have no active firewall. The terminal warnings are also harmless and can be ignored.
Simon, thank you for testing. Can you repeat the tests after running
lpadmin -p Lexmark_ S300S400_ Series -R usb-unidir
This removes the forced uni-directional mode. Lexmark's proprietary driver needs bi-directional communication.
Don't worry about firewall warnings, this is a bug in Lexmark's installer, it probably does not recognize that you have no active firewall. The terminal warnings are also harmless and can be ignored.