Xenforum

Former product manager of web development here. This app is good. There is a bit of a learning curve to understand the entire setup. Overall, I'm satisfied. The support team so far is really good and responsive.
We were answering individual email questions from customers which took up a bunch of our time. Now our customers ask us questions publicly, we answer the questions publicly, and future customers can easily find answers to their questions without having to contact us directly. If you get a lot of direct email inquiries from customers, I highly recommend this app. The best forum on the Shopify App store.