No post included in sitemap

Hi, this I’ve not seen before. Is there any other plugin that filters feed content or anything like that?

yes:

// action
add_action('pre_get_posts', 'filtru_culturi_posts', 10, 1);

function filtru_culturi_posts( $query ) {
	
	// bail early if is in admin
	if( is_admin() ) return;
	
	// bail early if not main query
	// - allows custom code / plugins to continue working
	if( !$query->is_main_query() ) return;
	
	// get meta query
	$meta_query = $query->get('meta_query');
	
	// loop over filters
	foreach( $GLOBALS['filtru_culturi'] as $key => $name ) {
		
		// continue if not found in url
		if( empty($_GET[ $name ]) ) {			
			continue;
		}
		// get the value for this filter
		// eg: https://www.website.com/events?city=melbourne,sydney
		$values = explode(',', $_GET[ $name ]);
		foreach( $values as $value ) {
			$meta_query[] = array(
				'key' => $name,
				'value' => $value,
				'compare' => 'LIKE',
			);
		}
        
	} 
	// update meta query
	$query->set('meta_query', $meta_query);

}

You could use is_sitemap() available in XML Sitemap Feeds to bail this filter:

// bail early
if( function_exists('is_sitemap') && is_sitemap() ) return;