The *actual* way of getting CUPSD to share printers

Although modern cupsd documentation describes a couple of simple steps that should theoretically enable sharing of printers on your system, one critical component is missing.

Documentation on cups.org suggests using cupsctl and lpadmin to enable sharing of a printer; this is all fine and good:

cupsctl --share-printers
lpadmin -p printer -o printer-is-shared=true

Inside of the default cupsd.conf there is a section

  Allow @LOCAL
  Order deny,allow

You need to add the Allow @LOCAL line in order to enable sharing from local subnets, which is probably the most common user case.

Afterward, restart the cups daemon.