it seems to have a plugin for federation, but I'm not sure how federation works for forums

It doesn’t, federation makes it not a web forum and its “web forum first” nature makes Discourse fundamentally unsuitable for things like technical work. (As opposed to, say, product support.)

If you want federation, set up a mailing list gatewayed to a usenet group you host on your own NNTP server, and slap a web forum interface on top of that for the whiny children who won’t use anything that isn’t inside a browser.