/usr/share/doc/gnustep-base-doc/Developer is in gnustep-base-doc 1.24.0-1ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/doc/gnustep-base-doc/../gnustep-base-common/Developer
/usr/share/doc/gnustep-base-doc/../gnustep-base-common/Developer