Mailchimp subscribe links, I did a little digging and you can create these in the free version (assuming I understood what you were wanting). These forms allow users to input their own information to subscribe to your Mailchimp updates. I made a quick example of one to test its functionality. CLICK HERE to view ours and see if this is what you're looking for.

I also created a little tutorial (CLICK HERE) for how to do it but let me know if you need additional help. I'd be happy to set up a call to walk you through it. You can use the link to generate a QR code for display like you mentioned.