Get min max value to range filter from query. New callback is added to the filters https://prnt.sc/5TxhF-B5wYGj

min_max_from_query.php

<?php

add_filter('jet-smart-filters/filter-instance/args', function ($args) {

	$filter_id = $args['filter_id'];
	$query_var  = get_post_meta($filter_id, '_query_var', true);
	$step = get_post_meta($filter_id, '_source_step', true);
	$source_cb = get_post_meta($filter_id, '_source_callback', true);
	$source_query = get_post_meta($filter_id, '_source_query', true);
	if (!$step) {
		$step = 1;
	}
	if (is_callable($source_cb)) {
		$data = call_user_func($source_cb, array('key' => $query_var . ',' . $source_query));
		$min  = isset($data['min']) ? $data['min'] : false;
		$max  = isset($data['max']) ? max_value_for_current_step($data['max'], $min, $step) : false;
		$args['min'] = $min;
		$args['max'] = $max;
	}
	return $args;
});

function max_value_for_current_step($max, $min, $step){

	if ($step === 1) {
		return $max;
	}

	$steps_count = ceil(($max - $min) / $step);

	return $steps_count * $step + $min;
}

function custom_source_callback($args = array()){
	if (!function_exists('jet_engine')) {
		return $callbacks;
	}

	global $wpdb;

	$key = !empty($args['key']) ? $args['key'] : false;

	if (!$key) {
		return array();
	}

	$key_parts = explode(',', $key);

	if (count($key_parts) !== 2) {
		return array();
	}

	$field = trim($key_parts[0]);
	$query_id = trim($key_parts[1]);

	// Use a macro to get post IDs
	$macro_result = jet_engine()->listings->macros->do_macros('%query_results|' . $query_id . '|ids%');

	if (is_string($macro_result)) {
		$post_ids = explode(',', $macro_result);
	} else {
		$post_ids = $macro_result;
	}

	$post_id_condition = '';
	if (!empty($post_ids)) {
		$post_id_condition = " AND p.ID IN (" . implode(',', $post_ids) . ")";
	}

	$sql = "SELECT min(FLOOR(pm.meta_value)) as min, max(CEILING(pm.meta_value)) as max
            FROM $wpdb->postmeta AS pm
            INNER JOIN $wpdb->posts AS p ON p.ID = pm.post_id
            WHERE pm.meta_key IN ('" . str_replace(',', '\',\'', str_replace(' ', '', $field)) . "')" . $post_id_condition;

	$data = $wpdb->get_results($sql, ARRAY_A);

	if (!empty($data)) {
		return $data[0];
	} else {
		return array();
	}
}

add_filter('jet-smart-filters/range/source-callbacks', function ($callbacks) {
	if (!function_exists('jet_engine')) {
		return $callbacks;
	}
	$callbacks['custom_source_callback'] = __('Get from JetEngine Query', 'jet-smart-filters');
	return $callbacks;
});

Thank you for this function.

Just for info: I had to change:
$data = call_user_func($source_cb, array('key' => $query_var . ',' . $source_query));

into
$data = call_user_func( $source_cb, array( 'key' => $query_var ) );

to get it working. Otherwise $min and $max would always be false.

I also checked the database. The filter does not have a post_meta field _source_query.

Best regards
Stef

New version https://gist.github.com/JuliaKiselyova/6832a7ec743e2aa3c7299556cb0e7ebd