BuddyPress.org

thanks.

you mean the discussion topics shown at the bottom of the home page.

well, I am using external bbpress with deep integration to buddypress/wordpress mu.

The topics are coming from https://wordpress.org/extend/plugins/bbpress-latest-discussion/ plugin.

Though, if you want to do the same using internal integration

have a look here

https://codex.buddypress.org/developer-docs/custom-buddypress-loops/the-activity-stream-loop/

specifying the action as “new_forum _post” should do that.

Hope it helps