If you want your static html to process a form, a few years ago the simplest approach was to add a php file to your site. Nowadays it is to create a zap webhoo

If you want your static html to process a form, a few years ago the simplest approach was to add a php file to your site. Nowadays it is to create a zap webhook and point your form there. My point was that this is not and has never been a complex thing requiring a framework or a complex backend.