Steps to reproduce the issue

Install locally Joomla 4.1.2 in PHP 8.1

Expected result

Normal installation page

Actual result

A message is displayed in the top of the page like this bellow

Deprecated
: Return type of Joomla\Input\Input::count() should either be compatible with Countable::count(): int, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in
D:\laragon\www\joomla4\libraries\vendor\joomla\input\src\Input.php
on line
149

System information (as much as possible)

Laragon with PHP 8.1.4, Maria DB 10.6.4 and Apache 2.4.51

Additional comments