In both the Dashboard and the published blog page, WordPress organizes the list of users alphabetically according to first name. I would like the list to appear alphabetically by LAST name, at least on the published blog page, even if not in the Dashboard. How would I be able to make this re-ordering
Your site is not hosted with us on WordPress.com, but using the open source WordPress software found on WordPress.org. Support for that version of WordPress can be found at https://wordpress.org/support/
That said, the ordering of users on a site depends on the usernames set in the dashboard, not the nicknames or the first/last names. I don’t think there is a way to change this, but if there is the users in the WordPress.org forums should be able to tell you how.