php 7.3

Fatal error: Uncaught TypeError: Argument 1 passed to XF\Extension::__construct() must be of the type array, bool given, called in /var/www/mc-security/src/XF/App.php on line 1452 and defined in /var/www/mc-security/src/XF/Extension.php:12 Stack trace: #0...

I am currently running Xenforo on what I believe is version 1.5.1. If I select PHP Version 7.3, it returns that there are server errors, and the forum is inaccessible. When a version below 7.3 is selected, things start to work properly again. Is this a known incompatibility? A separate issue is...