Finding Slack users/communities

Hi everyone, My cofounder and I are working on a few Slack app ideas and we've been looking for ways to find Slack community admins. We've found quite a few that run communities for websites and public groups... ... but we're struggling finding communities/employers that actually pay for Slack. I'm curious how other folks have tried to build apps for the Slack ecosystem and found initial users (beyond the Slack marketplace, of course). Happy to share info about my app if people are curious as well, but I wanted to keep this less about us and more about the problem. Thank you, Wojciech