We have a two-sided marketplace currently with a single buy-side community and are migrating to a model with a number of private buying groups. Each of these groups needs their own private communication mechanism and I'm trying to figure out some options to keep everything within the site.
Something like you see in Meetup.com, although maybe a more modern version (e.g., like an embedded Slack). Has anyone either seen sites that do this well or, for extra credit, software/services that make it easy to extend existing sites?