Free Mailchimp- how to offer a reader magnet?

I'm trying to set up a popup for my website using Mailchimp, but all of the how-to info I can find seems to be outdated, because apparently as of June 1st, 2025, they no longer offer many of the features in the free version that they used to.

I created a children's picture book to use as a reader magnet in both PDF and EPUB formats. I think I'm adding the urls in the right place when I'm setting up the popup, but I don't think it's working. Sorry if this is too technical for this platform. I'm guessing more of you might run into it, though. Paying for the upgraded version doesn't feel like a good option right now, since I have a grand total of zero subscribers, and no contracts in the making or books to sell yet.

Are there any good alternatives to Mailchimp? I discovered a WordPress plug-in, Mail Munch, that seems to be connected with Mailchimp. Does anyone have experience with that? Is it free? (Sorry, Thomas Umstattd, I can't get a job right now!)

I have the Mailchimp popup working as in popping up, but I don't think it's collecting email addresses or sharing the download. If anyone wants to try it and let me know, that would be amazing! You may definitely unsubscribe then.

Also, is there a quick answer to this question? How do you connect a reader magnet to a single “download here" button, is that possible? Through Mailchimp again? A plug-in? Or Divi? I should probably just ask Gemini.

What about double opt-in and Re-catchpa or whatever that's called? Are those possible only through an email automation? I can't figure out whether I can set that up with /the free version of Mailchimp.

Thanks to anyone who has knowledge to address any of my floundering cluelessness! :D