/usr/lib/x86_64-linux-gnu/libXmHTML.so is in xmhtml1-dev 1.1.7-19.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libXmHTML.so.1
/usr/lib/x86_64-linux-gnu/libXmHTML.so.1