I am so very sorry to have not replied for so long. I went to a five day homesteading, agricultural conference that had terrible Internet connectivity and poor phone service. It was restful but... I was not able to reply.
I agree with both of you that we should NOT mess with core joomla.
I am using 4SEF. But, they can't change the URLs to overcome this problem because they always make links to categories with a / at the end. But, the SP Page Builder pages are being created without the / at the end. I personally prefer not having the / at the end. But, as far I can tell there will always be a category url page created by Joomla and an SP Page builder link for the same page that has a completely different URL. That is how it is on your Quickstarts as well.
There must be something I am doing terribly wrong with the SP Page Builder because I seem completely unable to get the SP Page Builder pages to replace the Category pages. I have always been able to do this with other third party software like the EasyBlog, EasytSocial, EasyDiscuss software and others. But, I can't do this with SP Page Builder. Perhaps this is a feature and not a bug but my site is very broken because of this.
4SEF is creating the URLs to the 'category' page links in the RAXO modules on our homepage with a / at the end and, I understand that is something that they will not be changing because the urls ending in / is how they differentiate categories, and probably form the URLs for the articles assigned to the categories. All of the Menu items on our site are are buidling the URLs to our PAge Builder pages without the / at the end. We love that.
So, for example the links to the L'Chaim menu item is
https://test1.theraliv.org/lchaim
(notice no slash at the end. I am assuming those urls are NOT created by 4SEF. But, they are the URLs I am wanting to use. If you look at that page it is a Page Builder page with RAXO modules.
The links to the L'Chaim category from the RAXO modules on the home page is
https://test1.theraliv.org/lchaim/
(Those links are certainly being created by 4SEF because they change if I don't use the the option for Process Mode of "Normal". If you look at that page you will see a Joomla component page displaying the Gazette template page. This is the page we do not want because we were expecting to have the SP Page Builder page replace it.
Anyhow, my team has to make the tough decision now between abandoning the Category Names and links on the home page or abandoning SP Page Builder and just recreating our pages using the Gazette template without using SP Page Builder. It is a sad choice to have to make.