I'm a huge Crystal fan and spoke at the first user conference recently about my project which is almost what you're asking for: https://nlh.me/projects/celesti

I'm a huge Crystal fan and spoke at the first user conference recently about my project which is almost what you're asking for: https://nlh.me/projects/celestite https://nlh.me/projects/celestite It's a way to tightly integrate Crystal + Svelte, including server-side rendering and the ability to write your frontend purely from components. Not React (yet), but it's heading in that direction...