Pop up subscription modal

Hi, I’d like to create pop up subscription modal similar to this one https://campaignresources.phe.gov.uk/schools#subscribeModal. Looking through the forum I have found several posts recommending outside apps to achieve this rather than creating directly in Webflow. However, these posts are a few years old so wondered what’s the best way now?


Here is my public share link: LINK
(how to access public share link)