My understanding is that content categorization here is based on tagging, so you would look for #mechanicalkeyboard, #mechkb, or #ripster.
It's a little more free form, which makes it harder for a community to agree on a category name, but maybe there's tag suggestions - I don't know, haven't made a post yet. It is cool that the system apparently supports multiple tags on a post though, so you can effectively not have to worry about crossposts and split discussions.
Made yourself an ergodox? Tag as #mechkb and #maker and both groups get to talk together.