For my 12 year side project, I recently moved from Elastic Beanstalk after 6-7 years to Platform.sh, because "it just works" even more so and it was way easier to debug (EB just says "error in step 18_install_yarn" or something).
I use Symfony (Php) and have not used a full SPA after I retired AngularJS (v1) like 10 years ago. What people now call server side rendering (SSR) is just how Symfony works with its regular Twig templating language (heavily inspired by Django's templating language).
As I gained more experience, I rewrote it. Once from vanilla PHP to Laravel, then later to Symfony.
But maybe Symfony would be something like Linux Debian, has all the building blocks, it's modern but stable and well documented. Laravel is like Linux Ubuntu, it bases many things on Debian, but adds many things to make stuff a bit easier for the user. It's "shinier" and it has better marketing. You can add Debian stuff to Ubuntu, but you can't necessarily add Ubuntu stuff to Debian.
Symfony is more modular, you can add the components to any PHP project. Whereas Laravel uses many Symfony components and adds some syntactic sugar, but once you go into Laravel, it's difficult to stray away too far from the "Laravel way". Laravel uses many Symfony components, but Symfony can't easily use Laravel components.
Self-hosted Wordpress would maybe be comparable to a rooted Android phone. It has a very specific use case (for Wordpress it's fundamentally a Content Management System). You can add all sorts of plugins and additions. But it's also easy to accidentally break something. And once you added too many things, it might be difficult to update without breaking many things.
In the end, they're all Linux based, but living in very different ecosystems (just as Symfony, Laravel and Wordpress are PHP-based).
In programming terms, Symfony might be similar to Django (Python) or Spring Boot (Java), whereas Laravel is "cousins" with Ruby on Rails.
Server side rendering of React applications doesn't just refer to the fact that it's generated on the server like you do with PHP.
The main difference is that there are IDs that allow the client side code to seamlessly attach event handlers (this is called hydration) to the DOM - and that there is no difference between server and client side code.
In your case, you'd have to do that manually - a huge difference (speaking as someone who used to do that with jQuery).
I use Symfony (Php) and have not used a full SPA after I retired AngularJS (v1) like 10 years ago. What people now call server side rendering (SSR) is just how Symfony works with its regular Twig templating language (heavily inspired by Django's templating language).
As I gained more experience, I rewrote it. Once from vanilla PHP to Laravel, then later to Symfony.