\Magento\Framework\Config\Reader\Filesystem::_createConfigMerger() uses the «new» keyword instead of the Object Manager even after the Object Manager has already been initialized, so it breaks a dependency injection possibility

See also Magento 2 ignores XML schema location in the etc/adminhtml/system.xml documents and always uses the Magento/Config/etc/system_file.xsd schema instead

A partial solution for my particular case: How to change a constructor argument’s value with the depenency injection.

It is still not fixed in Magento 2.4.7-beta1: