/usr/share/man/man1/aarch64-linux-gnu-gnathtml.1.gz is in gnat-5-aarch64-linux-gnu 5.5.0-12ubuntu1cross1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/man/man1/aarch64-linux-gnu-gnathtml-5.1.gz