I think I have figured it out.
I have created several separate menus dedicated to each of the joomla article categories, and have made a menu item for each article in the category. A bit of work to say the least. Even though this menu is effectively 'hidden', the "Articles" Addon list in SP Page Builder is now working and linking correctly.
For places that I am using a link directly in a SP Page Builder page, such as a text link, a button, heading, well, really most any Addon in SP Page Builder, you have to remember the structure of the link and put it in manually.
I have often wondered, and still wonder, why JoomShaper only allows for hard linking/absolute URLs in their Addons. This is a significant pain and increases effort and time spent by a lot.
If you could consider building into your Addons the option of selecting from a joomla menu item instead of just using a hard link, that would be significant.
As a side note, having the ability to link to a joomla menu item also comes with the (not so small) benefit of being able to change the SP Page Builder Page name "after the fact", or make a correction to the Page name and Joomla will automatically keep the link intact. Using absolute URLs/hard linking, it just breaks.
Thank you for your consideration.