Svelte is a very clean frontend framework that needs a lot less rituals than, say, react to do what you need it to do. Your backend send data (JSON) and svelte renders it.
Unpoly is designed for your backend to send HTML and unpoly (among other things) avoids full page reloads when you navigate to another page. It has some other very nice functionality that, if included from the beginning in the architecture, can completely avoid needing a frontend framework.