Current behaviour:

Currently Confluence automation doesn't have a trigger for when public links are enabled.
https://support.atlassian.com/cloud-automation/docs/triggers-in-confluence-automation/ 

Ask:
Site admins/space admins would like to have a trigger in Automation for when "Public links are enabled" which can used to create an Automation rule to send an email to users when Public links are enabled.

Benefit:
This will be crucial in terms of security as enabling Public links on pages make the pages available for anyone with the links and needs visibility on the same.