Does not list pages for a category

Are you saying it does not create a list of the Posts or that the Posts are not displayed? There are settings so you can customize the display.

My categories can contain both posts and pages.
When a category is selected in the settings, the plugin seems to show only posts; the pages do not show up on the list ??
I could not find a setting that would control that and include the pages on the list of the displayed entries.

I have not seen Pages that are Categorized. Learn something new here. Curious what additional do you get from setting a page as a category? Can you show the url?

I use the plugin “Add Categories to Pages.”
Example: https://livingoffcloud.com/smart-banking/

I see now. The thing is the Recent Post widget shows “Posts”. It works with the base WP core. It would be hard for someone to write a widget based on the functionality of another widget as opposed to the actual WP program.
There are various benefits of adding category to Pages You can
* Embed a Category Based List of Pages
Based on the above, the Add Category to Page may have the functionality your looking for.

This plugin shows only WP posts. You can display both post and pages of specified categories with my plugin Ultimate Post List Pro. If that does not work you will get support by me or your money back (within 14 days after purchase).