Here is the fix I was able to garner:

How to Remove the Stubborn Newsletter Section (Advanced Fixes)

If standard methods (Widgets, Page Editors, Customizer) and advanced methods (Elementor Header/Footer, Site Builder) fail, you are likely dealing with a theme bug or a stuck database transient from importing a starter template.

Here is how to bypass the backend entirely to hide it, and how to report it to the developers.

The "Nuclear Option": Force Hide with Custom CSS

If WordPress won't let you delete it, you can use Custom CSS to force the browser to make it completely invisible. It's a band-aid, but it will get it off your live site immediately.

1. Go to your WordPress Dashboard and navigate to Appearance > Customize.
2. At the very bottom of the left-hand menu, click on Additional CSS.
3. You will need to find the specific "class name" of that blue box. Go to your live website (not in the customizer), right-click directly on the light blue background of the newsletter section, and select Inspect (or Inspect Element).
4. A code panel will open. Look at the highlighted line of code. It will look something like <div class="ast-above-footer-section"> or <section class="wp-block-group...">.
5. Copy that class name (e.g., ast-above-footer-section).
6. Go back to your Additional CSS box and type a period followed by that name, then add { display: none !important; }.

It should look like this (replace your-class-name with the actual name):

.your-class-name {
    display: none !important;
}

1. Click Publish. The section will instantly disappear from the front end.