I am curious how would you create a quote template through html, the inbuilt template don't appear to have this functionality.
Visualforce cannot render HTML on CPQ quote templates. To get anything to show at all from a Rich Text field you will need to use HTMLENCODE() function in Visualforce and this will prevent rendering. Otherwise it will just output blank text. Use Conga or another Quote Template tool if you need to show HTML via Visualforce in CPQ Quote Templates.