Start with your personal social circle, and/or 1st level referrals from your personal social circle. It's what Steve Blank calls "Friendly First Contacts". If you can't figure out a way to get useful feedback / sign of a reason to move forward from this group, then pivot or give up.
The other option is "spend money to blast your thing to a wide audience and hope for the best." Buy Reddit ads, Facebook ads, LinkedIn ads, Google ads, whatever. The downside to this is: it costs money (potentially a lot) and doesn't generate necessarily generate quality feedback because the people you're targeting aren't invested in helping you.
Also: read The Four Steps to the Epiphany or The Startup Owner's Manual.
The other option is "spend money to blast your thing to a wide audience and hope for the best." Buy Reddit ads, Facebook ads, LinkedIn ads, Google ads, whatever. The downside to this is: it costs money (potentially a lot) and doesn't generate necessarily generate quality feedback because the people you're targeting aren't invested in helping you.
Also: read The Four Steps to the Epiphany or The Startup Owner's Manual.