Steps to reproduce the issue

Update from version 4.0.3 to version 4.0.5

Expected result

Removed the Deprecated warning when you put to maximum the error_reporting flag

Actual result

Among others, show mainly these warnings in all page including the administration pages:

Deprecated
: Return type of FOF40\Pimple\Container::offsetExists($id) should either be compatible with ArrayAccess::offsetExists(mixed $offset): bool, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in
libraries/fof40/Pimple/Container.php
on line
131

Deprecated
: Return type of FOF40\Pimple\Container::offsetGet($id) should either be compatible with ArrayAccess::offsetGet(mixed $offset): mixed, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in
libraries/fof40/Pimple/Container.php
on line
95

Deprecated
: Return type of FOF40\Pimple\Container::offsetSet($id, $value) should either be compatible with ArrayAccess::offsetSet(mixed $offset, mixed $value): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in
libraries/fof40/Pimple/Container.php
on line
75

Deprecated
: Return type of FOF40\Pimple\Container::offsetUnset($id) should either be compatible with ArrayAccess::offsetUnset(mixed $offset): void, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice in
libraries/fof40/Pimple/Container.php
on line
142

System information (as much as possible)

PHP 8.1.0
Joomla 4.0.5