BuddyPress.org

I’ve achieved what I wanted. Most likely in an incredibly convoluted way.

If anyone can see any glaring issues with my code please shout. I’m a ludite when it comes to querying databases, arrays, etc.

// Create the array for post ids related to the users industry
		
	global $wpdb;
	$industry = xprofile_get_field_data( 2, $user_id, false );
	$metas = $wpdb->get_results ( "SELECT activity_id FROM wp_bp_activity_meta WHERE meta_value='$industry'" );
	$metasjson = json_decode( json_encode($metas), true);
	
		
	$newList = array();
foreach($metasjson as $key=>$listItem) {
 $newList[$key] =  $listItem['activity_id'];

} 

Then I added the below to your $retval

// Get Posts in Specified Category
		array(
			'relation' => 'AND',
			array(
				'column'  => 'id',
				'compare' => 'IN',
				'value'   => (array) $newList
			)
		),