I just tried upgrading from 2.4 to 2.4.1 and now the site is down.
We get this error only when trying to access the admin
{"0":"Type Error occurred when creating object: Magento\Framework\Session\Generic\Interceptor, setcookie() expects
parameter 3 to be integer, array given","1":"#1
Magento\Framework\ObjectManager\Factory\Compiled->create('Magento\Framewor...') called at
[vendor/magento/framework/ObjectManager/Factory/Compiled.php:150]n#2
Magento\Framework\ObjectManager\Factory\Compiled->get('Magento\Framewor...') called at
[vendor/magento/framework/ObjectManager/Factory/Compiled.php:79]n#3
Magento\Framework\ObjectManager\Factory\Compiled->create('Magento\Framewor...') called at
[vendor/magento/framework/ObjectManager/Factory/Compiled.php:150]n#4
Magento\Framework\ObjectManager\Factory\Compiled->get('Magento\Framewor...') called at
[vendor/magento/framework/ObjectManager/Factory/Compiled.php:79]n#5
Magento\Framework\ObjectManager\Factory\Compiled->create('Magento\Framewor...') called at
[vendor/magento/framework/ObjectManager/Factory/Compiled.php:150]n#6
Magento\Framework\ObjectManager\Factory\Compiled->get('Magento\Framewor...') called at
[vendor/magento/framework/ObjectManager/Factory/Compiled.php:79]n#7
Magento\Framework\ObjectManager\Factory\Compiled->create('CsrfRequestValid...') called at
[vendor/magento/framework/ObjectManager/Factory/Compiled.php:150]n#8
Magento\Framework\ObjectManager\Factory\Compiled->get('CsrfRequestValid...') called at
[vendor/magento/framework/ObjectManager/Factory/Compiled.php:125]n#9
Magento\Framework\ObjectManager\Factory\Compiled->parseArray(array('csrf_validator' => array('_i_' =>
'CsrfRequestValid...'), 'http_method_vali...' => array('_i_' => 'Magento\Framewor...'))) called at
[vendor/magento/framework/ObjectManager/Factory/Compiled.php:86]n#10
Magento\Framework\ObjectManager\Factory\Compiled->create('RequestValidator') called at
[vendor/magento/framework/ObjectManager/ObjectManager.php:70]n#11
Magento\Framework\ObjectManager\ObjectManager->get('RequestValidator') called at
[vendor/magento/framework/App/FrontController.php:86]n#12
Magento\Framework\App\FrontController->__construct(&Magento\Framework\App\RouterList#0000000075152dce0000000037d45a14#,
&Magento\Framework\App\Response\Http\Interceptor#0000000075152d9b0000000037d45a14#, NULL, NULL, NULL, NULL, NULL)
called at [generated/code/Magento/Framework/App/FrontController/Interceptor.php:14]n#13
Magento\Framework\App\FrontController\Interceptor->__construct(&Magento\Framework\App\RouterList#0000000075152dce0000000037d45a14#,
&Magento\Framework\App\Response\Http\Interceptor#0000000075152d9b0000000037d45a14#, NULL, NULL, NULL, NULL, NULL)
called at [vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php:121]n#14
Magento\Framework\ObjectManager\Factory\AbstractFactory->createObject('Magento\Framewor...',
array(&Magento\Framework\App\RouterList#0000000075152dce0000000037d45a14#,
&Magento\Framework\App\Response\Http\Interceptor#0000000075152d9b0000000037d45a14#, NULL, NULL, NULL, NULL, NULL))
called at [vendor/magento/framework/ObjectManager/Factory/Compiled.php:108]n#15
Magento\Framework\ObjectManager\Factory\Compiled->create('Magento\Framewor...') called at
[vendor/magento/framework/ObjectManager/ObjectManager.php:70]n#16
Magento\Framework\ObjectManager\ObjectManager->get('Magento\Framewor...') called at
[vendor/magento/framework/App/Http.php:115]n#17 Magento\Framework\App\Http->launch() called at
[vendor/magento/framework/App/Bootstrap.php:263]n#18
Magento\Framework\App\Bootstrap->run(&Magento\Framework\App\Http\Interceptor#0000000075152d9d0000000037d45a14#)
called at
[pub/index.php:40]n","url":"/","script_name":"/index.php","report_id":"2a042cc9bf44183e0a485aa0ea00a58ca7ba84330b2acae02e570093fd1c26c6"}
Is this related to Support for the SameSite attribute for cookies that was introduced in 2.4.1?