What are you using to collect emails on your landing page or what engine are you using to host your landing page (Wordpress, dedicated SaaS or other)?
Have you tried Tally? You can embed forms for free on your page: https://blog.tally.so/embed-your-form/
i was using simple stuff like mailchimp or convert kit or formstack... don't need anything crazy, right?
you could even use substack in a way and definitely product hunt ship.
Another vote for MailChimp here to collect emails and I am using Dorik for building my landing page.
I'm using getwaitlist.com for my product (MDX.one).
It also has referral system built in to it.
We've been using unbounce (unbounce.com) for this for years. Also makes setting up a/b tests super easy + lots of integration options including zapier
I have a simple Rails API that I built for all my email collection across multiple sites/apps. I made sure to build it so it has confirmation as well, so random people can't sign up others' emails.