/usr/share/sgml/html/dtd/ is in sgml-data 2.0.6.
This file is owned by root:root, with mode 0o755.
..
/usr/share/sgml/html/dtd/4.0/
/usr/share/sgml/html/dtd/4.0/HTML4.decl
/usr/share/sgml/html/dtd/4.0/catalog
/usr/share/sgml/html/dtd/4.0/frameset.dtd
/usr/share/sgml/html/dtd/4.0/loose.dtd
/usr/share/sgml/html/dtd/4.0/strict.dtd
/usr/share/sgml/html/dtd/4.01/
/usr/share/sgml/html/dtd/4.01/HTML4.decl
/usr/share/sgml/html/dtd/4.01/catalog
/usr/share/sgml/html/dtd/4.01/frameset.dtd
/usr/share/sgml/html/dtd/4.01/loose.dtd
/usr/share/sgml/html/dtd/4.01/strict.dtd
/usr/share/sgml/html/dtd/catalog
/usr/share/sgml/html/dtd/html-0.dtd
/usr/share/sgml/html/dtd/html-0s.dtd
/usr/share/sgml/html/dtd/html-1.dtd
/usr/share/sgml/html/dtd/html-1s.dtd
/usr/share/sgml/html/dtd/html-2-i18n.decl
/usr/share/sgml/html/dtd/html-2.1e.dtd
/usr/share/sgml/html/dtd/html-2.decl
/usr/share/sgml/html/dtd/html-3.2.decl
/usr/share/sgml/html/dtd/html-3.2.dtd
/usr/share/sgml/html/dtd/html-3.decl
/usr/share/sgml/html/dtd/html-3.dtd
/usr/share/sgml/html/dtd/html-3s.dtd
/usr/share/sgml/html/dtd/html-970421.decl
/usr/share/sgml/html/dtd/html-970421.dtd
/usr/share/sgml/html/dtd/html-hj.dtd
/usr/share/sgml/html/dtd/html-hjs.dtd
/usr/share/sgml/html/dtd/html-mcom.dtd
/usr/share/sgml/html/dtd/html-mcoms.dtd
/usr/share/sgml/html/dtd/html-s.dtd
/usr/share/sgml/html/dtd/html.dtd
/usr/share/sgml/html/dtd/ie-2.0-tables.dtd
/usr/share/sgml/html/dtd/ie-2.0.dtd
/usr/share/sgml/html/dtd/ie-2.0s.dtd
/usr/share/sgml/html/dtd/ie-3.0-tables.dtd
/usr/share/sgml/html/dtd/ie-3.0.dtd
/usr/share/sgml/html/dtd/ie-3.0s.dtd
/usr/share/sgml/html/dtd/iso-15445/
/usr/share/sgml/html/dtd/iso-15445/15445.dcl
/usr/share/sgml/html/dtd/iso-15445/15445.dtd
/usr/share/sgml/html/dtd/iso-15445/catalog