It is possible to use your fediverse account to create a new topic.

This could be, for example, using your own Mastodon account, or GoToSocial, or Misskey, etc.

To achieve this, mention the fediverse address of the category in your post in your own server post. Example: @general-disussion@thefedi.forum

All posts are public, including your fediverse address.

(The addresses appear in the description for each category)