Hi after update you can have some error on old custom template, that normal your code need to be update for joomla4
in item.php or item_html5.php
In Joomla 3
find
JFactory::getDocument()->addScriptVersion(JUri::base(true).'/components/com_flexicontent/assets/js/tabber-minimized.js', FLEXI_VHASH);
JFactory::getDocument()->addStyleSheetVersion(JUri::base(true).'/components/com_flexicontent/assets/css/tabber.css', FLEXI_VHASH);
JFactory::getDocument()->addScriptDeclaration(' document.write(\'<style type="text/css">.fctabber{display:none;}<\/style>\'); '); // temporarily hide
find
JRequest::getCmd('print'))
In Joomla 4 remplace it for
find
JFactory::getDocument()->addScript(JUri::base(true).'/components/com_flexicontent/assets/js/tabber-minimized.js', array('version' => FLEXI_VHASH));
JFactory::getDocument()->addStyleSheet(JUri::base(true).'/components/com_flexicontent/assets/css/tabber.css', array('version' => FLEXI_VHASH));
JFactory::getDocument()->addScriptDeclaration(' document.write(\'<style type="text/css">.fctabber{display:none;}<\/style>\'); '); // temporarily hide the tabbers until javascript runs
find
JFactory::getApplication()->input->getCmd('print')