How do you add an embedded email signup form in a web app (React)?

Hello Indie Hacker Devs,

I'm trying to add email sign-up forms in react – both inside a React app and also on my landing page with is built with Gatsby (and therefore React).

I currently see two ways to do this, but neither seems great so I wanted to see what solutions others may have.

Here are my goals:

• I want the embedded email signup form to look like a seamless part of my website, which means matching the CSS styling, no iframes, no popups
• I want to keep the user on my site using an async javascript call – so no submitting a form that goes to an email service provider's (ESP) signup page

I haven't picked an ESP yet, but I'm looking at Mailerlite, EmailOctopus, and Sendinblue. I've used Mailchimp in the past which I'm trying to avoid for now.

The two solutions I have are:

1. Take the email signup embed code from the ESP, remove all CSS styling, react-ify the code (e.g. turn class into className, for to htmlFor, etc.), add the ESP's javascript <script> tag using react-helmet, and add any dom-attached javascript code with useEffect (e.g. document.body.appendChild(script)). This works pretty well, though I'm not a fan of including external scripts. Mailchimp's js script is huge and Mailerlite uses jQuery which I don't want to include unless I have to.

2. Use a serverless function to take email signup submissions and send the data to the ESP via their API. I'm using Firebase so I could have my website/app send the email signup data to a Firebase Cloud Function to do this. The good thing is now I have total control over the email signup flow. But the problem is now I have to maintain a cloud function, there is an extra moving part that can break, and I have to either manually deal with error/success messages or relay the error/success messages from the ESP's API through the cloud function and back to the web app.

All of this above seems way too complicated for an email signup form, so I'm just trying to figure out if I'm missing something obvious.

How do you handle this?

Any help is much appreciated.

Thanks!