Solo founders: how did you find your first 10 users who actually gave useful feedback?

I've tried Reddit posts, a few Discord communities, and cold DMs. Most responses were polite silence. The few people who did respond gave feedback that was too vague to act on. "Looks cool." "Nice idea." Nothing that changed what I built.

The problem isn't finding people it's finding people who care enough to tell you something uncomfortable.

So for those who got past this stage: where did your first 10 users who actually gave actionable feedback come from? Not "post on Twitter," a specific channel, a specific approach, a specific thing that worked. And the harder follow up: what did you do with the vague feedback before you found the useful feedback?