There are free discussion sites out there that still operate kind of under the social media radar. I was a member of a discussion group that focused on stage and film actors that has been moved from one site to another as they buy each other out. If you use it free, it has a lot of ads. It isn't terribly expensive to have a paid account and remove the ads. All of the topics are threaded.

Tapatalk.com. I'll send you a PM with a link to my (all but defunct) group so you can poke through the threads for an example of how it works.