If a user it directed to a page which requires login, I would like to either redirect the user to the login page or add a login block to that page.
There are Drupal 7 modules to accomplish this. What do we have for Backdrop at this time (either in Backdrop CMS core or in contrib modules)?
OK, I found the 'Redirect 403 to User Login' module:
https://backdropcms.org/project/r4032login
This does exactly what I was looking for.
(Posted this as @klonos was posting an information response. Thanks Gregory).