After quick start install and Joomla update to 4.1.3 this is the result:
Blank page apart from this message:
templates/sj_royal/templates/system/css/general.css not exists

Dear aegir,

In the file: /templates/sj_royal/includes/frame_inc.php
Please remove this code:
$yt->ytStyleSheet('templates/system/css/general.css');

Thanks

Hi Thuygtn

Thanks for a quick reply.

I removed the code you suggested, but there is still some issue:
404 Error Call to undefined function split()
(can't add an attachment).

I updated the French and the German, and the YTshortcodes (_j4x_v4.zip) but I could not update the SJ Content Categories (error: 0 Undefined constant "JPATH_"

Kind regards
Aegir

Dear aegir,

Can you send your site account (URL and admin + FTP) in 'For Staff only' field when you reply? I will check your issue asap.

Thanks