@Crell Thank you, for reply. I watched your talk yesterday on #phpverse It was great!
You probably mean https://www.php.net/manual/en/class.dom-htmldocument.php and Dom/Xpath. I had the same problem there, and I switched back to 8.3 before finding out my error. I'll write some comments to php.net to let others, with same presumptions as me, know.