Q&A plugin appears to be adequate, but does not have downvotes. Downvotes are important, as a knowledgeable person should ideally be able to downsize bull****. This is important for collaborative learning - and should be developed to approach the usefulness of Stack Exchange and Reddit. Would need to put development time into this.
Bug Tracking - a simple wiki/Discourse hack can be done by a Bugtracking or Known Bugs category on the wiki, and embedding a thread on that bug from Discourse, so discussion can happen, and when resolved, thread can be closed. We'd have to see in practice how this looks. That is the simplest way to go without installing yet another pieces of software, and using Discourse and Wiki hold most of the weight, the rest being Wordpress.
In 2018-09, I (Michael Altfield) had just learned about Discourse as I was working on the phplist project. phplist's forums use Discourse. At the same time, Alex Au recommended to Marcin that we setup a replacement forum using Discourse.
ie: replace wordpress comments with a discourse thread. This may or may not be good.
Well-funded org that hosts their project (think wordpress.com) for many of their customers. The good here is that Discorse can pay a salary to devs, unlike many open source projects. But it's worth nothing that people choose to pay for hosting probably because it's Ruby on Rails, and a PIA to self-host.