functions.php

<?php
  
/**
 * Display Posts, FacetWP Support
 * @see https://displayposts.com/2019/04/20/facetwp-support/
 *
 */
function be_dps_facetwp( $args, $atts ) {
	if( !empty( $atts['facetwp'] ) && filter_var( $atts['facetwp'], FILTER_VALIDATE_BOOLEAN ) )
		$args['facetwp'] = true;
	return $args;
}
add_filter( 'display_posts_shortcode_args', 'be_dps_facetwp', 10, 2 );

/**
 * FacetWP support in custom queries
 * @see https://facetwp.com/documentation/templates/wp-query/
 *
 */
add_filter( 'facetwp_is_main_query', function( $bool, $query ) {
    return ( true === $query->get( 'facetwp' ) ) ? true : $bool;
}, 10, 2 );