/usr/share/doc/linux-tools-generic-hwe-16.04/changelog.gz is in linux-tools-generic-hwe-16.04 4.15.0.20.23.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/linux-tools-generic-hwe-16.04/../linux-tools-generic/changelog.gz