/etc/apache2/conf.d/linkchecker.conf is in w3c-linkchecker 4.81-7.
This file is owned by root:root, with mode 0o777.
It is a symlink to /etc/apache2/conf.d/../../w3c/apache2-linkchecker.conf
/etc/apache2/conf.d/../../w3c/apache2-linkchecker.conf