It is not clear what exactly you are looking for?

> “Just post it on Hacker News or Reddit and show that people love it.”

From my experience, both HN and Reddit have the worst traffic. I got "tens of thousands" of visitors from both with exactly zero conversion. I am now getting a few hundreds a month from Google and other sources and the conversion rate is roughly 20-25%. So pretty much not worth it to pursue HN/Reddit for your startup though your mileage would probably vary.

I'd use HackerNews for what it is, a news site for casual/mixed information with sometimes interesting discussions. You could have much better levers in other places.