TemplateMo - TemplateMo is a great place to get bootstrap templates from your website, which are all HTML5 supported with CSS layout.
Tailwind UI Kit - 600+ components, 30 templates, React, Angular, & Vue support
Ethereal by HTML5 UP - A fully responsive side-scrolling one-page HTML5 template
Inovatik HTML Templates - Download 24 FREE HTML templates to help you create beautiful websites and landing pages faster.
UIdeck - Landing Page HTML Templates and UI Kits
Cruip - Landing page templates for startups