/usr/include/KF5/KHtml/ is in libkf5khtml-dev 5.28.0-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/KF5/KHtml/KHTMLPart
/usr/include/KF5/KHtml/KHTMLSettings
/usr/include/KF5/KHtml/KHTMLView
/usr/include/KF5/KHtml/dom/
/usr/include/KF5/KHtml/dom/css_rule.h
/usr/include/KF5/KHtml/dom/css_stylesheet.h
/usr/include/KF5/KHtml/dom/css_value.h
/usr/include/KF5/KHtml/dom/dom2_events.h
/usr/include/KF5/KHtml/dom/dom2_range.h
/usr/include/KF5/KHtml/dom/dom2_traversal.h
/usr/include/KF5/KHtml/dom/dom2_views.h
/usr/include/KF5/KHtml/dom/dom_core.h
/usr/include/KF5/KHtml/dom/dom_doc.h
/usr/include/KF5/KHtml/dom/dom_element.h
/usr/include/KF5/KHtml/dom/dom_exception.h
/usr/include/KF5/KHtml/dom/dom_html.h
/usr/include/KF5/KHtml/dom/dom_misc.h
/usr/include/KF5/KHtml/dom/dom_node.h
/usr/include/KF5/KHtml/dom/dom_string.h
/usr/include/KF5/KHtml/dom/dom_text.h
/usr/include/KF5/KHtml/dom/dom_xml.h
/usr/include/KF5/KHtml/dom/html_base.h
/usr/include/KF5/KHtml/dom/html_block.h
/usr/include/KF5/KHtml/dom/html_document.h
/usr/include/KF5/KHtml/dom/html_element.h
/usr/include/KF5/KHtml/dom/html_form.h
/usr/include/KF5/KHtml/dom/html_head.h
/usr/include/KF5/KHtml/dom/html_image.h
/usr/include/KF5/KHtml/dom/html_inline.h
/usr/include/KF5/KHtml/dom/html_list.h
/usr/include/KF5/KHtml/dom/html_misc.h
/usr/include/KF5/KHtml/dom/html_object.h
/usr/include/KF5/KHtml/dom/html_table.h
/usr/include/KF5/KHtml/kencodingdetector.h
/usr/include/KF5/KHtml/khtml_events.h
/usr/include/KF5/KHtml/khtml_export.h
/usr/include/KF5/KHtml/khtml_part.h
/usr/include/KF5/KHtml/khtml_settings.h
/usr/include/KF5/KHtml/khtmldefaults.h
/usr/include/KF5/KHtml/khtmlpart.h
/usr/include/KF5/KHtml/khtmlsettings.h
/usr/include/KF5/KHtml/khtmlview.h