Some folks seem to believe I object to any client-side JS in principle. I don’t. You might be on the wrong track if you find yourself having to do the same stuff on the server, though. SSR and CSR should complement each other, with SSR as the first and safer choice.
Here’s a mind-blowing idea: Instead of adding server-side rendering by getting your client-side framework to work on the server, too, first start with server-side rendering and make it really, really fast; then as a next step, maybe don’t do that client thing.