I would like for recent upload activity to display in our Buddypress activity stream, but it doesn't seem to work.
The BuddyPress activity will only be generated for the media which are uploaded to user profile media. ( i.e. under Media tab ).
The media uploaded to a particular post context will not have the context set as profile and hence the activity won't be generated for them.
Regarding your current shortcode:
[rtmedia_gallery context=event context_id=#_EVENTPOSTID media_type=photo media_title=false privacy=0 uploader=after]
The shortcode you are using has the context set as "event" which is incorrect. If you want to upload and display media on a post then use the
So, the shortcode would look like this:
[rtmedia_gallery context=post context_id=post_id media_type=photo media_title=false privacy=0 uploader=after]
You can find out more details here - https://rtmedia.io/docs/features/shortcodes/