since it is public forum as requested, there is no need for me to send invitations. I think it's better if you guys just reach out. You can also send an invites via discourse. And since it's public group I can't even assign users to it because every new user sees that group anyway and can participate.
New users should 'Mute' other public forums if they aren't interested, and 'watch' the ones that interests them. I guess it is explained in welcome message, but maybe we should stress that out more. (anyone feels like writing it? ).