You can try using a Block Element hooked to before_footer.
Then, using GenerateBlocks, you can use a GB Grid Block to create the two columns.
The left column would contain Headline Blocks, and yes, the right column would contain a WP HTML Block to embed the mailchimp form. I think Mailchimp also has a Shortcode. So, if it has one, you can use a WP Shortcode Block as an alternative as well.
I created the hook element. For now, I’m simply inserting a shortcode for the signup form. Not creating 2 columns at this point. But, I can’t get the “email subscribe” to show up above the very bottom footer. It’s showing up before the “leave a comment” section.
I’ve tried all the options for “generate before…” I don’t see an option to generate_before_footer_widgets.