Can confirm, that was the last project I worked on that had SSR; fancy product website / e-commerce, combined data from a CMS-as-a-service and a webshop-as-a-service, rendered pages in one go using Gatsby, published it. I believe that was the best of both (SSR / webapp) worlds, in that it was both fast and indexable in a static context, and if the user had JS enabled and the page was hydrated, navigation was super fast and lightweight because only some JSON went over the line.
I'm not sure if I would do it again though, but we'll cross that bridge when we get to it.
Why would you optimise for SEO on a webapp? What's the use-case there?
If you're not writing a webapp, then any server side rendering would do and client side components aren't needed anyway.