This is not true. You can pre-render shadow DOM with stencil - it has an option to generate a separate package which takes in HTML for components and outputs t

This is not true. You can pre-render shadow DOM with stencil - it has an option to generate a separate package which takes in HTML for components and outputs the shadow HTML ready for rehydration on client, including all the necessary CSS. This can be called on server before sending to client. Or at build-time for static sites.