Re: Buddypress sitewide forums
Reason why forums attached to groups https://codex.buddypress.org/buddypress-site-administration/buddypress-forum/
Others have installed WP forum plugins like: SimplePress forums, Mingle forums, WP Forum Server, etc. which works well. However, since the aforementioned forums are not integrated with BuddyPress, the participation in the forums are not recorded in member, group and sitewide activity components.
bbPress, which is integrated as the group forums for BuddyPress, is being configured as a stand-alone WP plugin
https://trac.bbpress.org/roadmap
Not sure how the integration with BP will be though. Maybe someone can chime in about this
There is a sitewide forums premium plugin that extends the bbPress currently installed via BP as a sitewide forum component. General Info about Global Forums by @sbrajesh here and here
