The html_file plugin was written many years ago and it has some horrible hard-coded HTML inside. This makes it really difficult to modify/improve the generated HTMLs.
* html_file: Improve plugin to use jinja2 templates #8866
* UnicodeDecodeError @ html_file: 'utf8' codec can't decode byte #4219
Plugin is working perfectly, just need to improve the template Improvements for HTML report template #8891