xprofile_update_display_names()

function xprofile_update_display_names() {
	$users = get_users( [
		'fields' => [ 'ID', 'display_name' ]
	] );

	foreach ( $users as $user ) {
		$display_name = bp_custom_display_name_format( $user->display_name, $user->ID );

		wp_update_user( $args = [
			'ID'           => $user->ID,
			'display_name' => $display_name
		] );
	}

	$statement = __( 'Update WordPress user display names; %s', 'buddyboss' );

	return array( 0, sprintf( $statement, __( 'Complete!', 'buddyboss' ) ) );
}