radio-sort.php

<?php

/**
 * filter html for sort output to output radio buttons
 */
add_filter( 'facetwp_sort_html', function( $html, $params ) {
    $html = '';
	foreach ( $params['sort_options'] as $key => $atts ) {
		$html .= '<input type="radio" name="custom-sort" value="' . $key . '">' . $atts['label'] . '<br>';
	}
	return $html;
}, 10, 2 );

/**
 * add js to custom handle selections of sort radio button
 */
add_action( 'wp_head', function() {
	?>
    <script>
        (function($) {
            $(document).on('facetwp-loaded', function() {
                $('input[type=radio][name=custom-sort]').change(function () {
                    FWP.extras.sort = $(this).val();
                    FWP.soft_refresh = true;
                    FWP.autoload();
                });
            });
        })(jQuery);
    </script>
	<?php
}, 100 );