ISPconfig 3.3.1 still uses SimplePie 1.2.1-dev (~2011), which is not php8 compatible. \ Strangely (to me at least) your own feed is shown without any problems (afaik), but the feed https://www.heise.de/security/feed.xml throws the following error: ``` PHP Fatal error: Uncaught Error: Non-static method SimplePie_Misc::atom_10_content_construct_type() cannot be called statically in /usr/local/ispconfig/interface/lib/classes/simplepie.inc.php:3349 ``` while the feed is not shown. Declaring the functions: ``` function atom_10_content_construct_type($attribs) function atom_03_construct_type($attribs) ``` as ``` public static function atom_10_content_construct_type($attribs) public static function atom_03_construct_type($attribs) ``` fixes that error and shows the feed.