It depends a lot on the target audience, but some subreddits also have a Slack/Discord channel where you can be more open about your intentions and get immediat

It depends a lot on the target audience, but some subreddits also have a Slack/Discord channel where you can be more open about your intentions and get immediate feedback. What I like about this model is that if any customer is really interested in your product, you can start a video call and discuss about it. Also, you can put these people on an email list of interested people (with their permission), which can be your first cohort.