I created simple system plugin to make it work (plugin should be ordered before artio system plugin):
<?php
defined('_JEXEC') or die;
// Own class - should be enabled because Artio JoomSEF fails and native Language Filter plugin is not enabled as required by Artio.
class JLanguageMultilang
{
public static function isEnabled()
{
return true;
}
}
class PlgSystemArtiofix extends JPlugin
{
public function onAfterInitialise()
{
$app = JFactory::getApplication();
// Not for Artio
if (isset($_GET['option']) && $_GET['option'] == 'com_sef')
{
return;
}
// Init associations, Artio JoomSEF fails and native Language Filter plugin is not enabled as required by Artio.
$app->item_associations = 1;
// We need to inject Language Filter instance, so JLanguageAssociations::isEnabled() will not fail.
$prop = new ReflectionProperty('JPluginHelper', 'plugins');
$prop->setAccessible(true);
$plugins = $prop->getValue();
$plugins[] = (object) array(
'type' => 'system',
'name' => 'languagefilter',
'params' => '{"item_associations":"1"}',
);
$prop->setValue($plugins);
}
}