Topics that covered this include:
I think @Canapin suggested searching on the standard FAQ text to find Discourse forums, e.g.:
https://www.google.com/search?q=This+is+a+Civilized+Place+for+Public+Discussion&ie=UTF-8&oe=UTF-8
Obviously that will not restrict you to CDCK hosted sites, just those sites who’ve retained that part of the standard FAQ included out of the box and are public.