You might not even need fancy techniques to have UX similar to a React app. When the page load is fast enough, browsers hide that it happened. This means you can afford to do everything in the backend and just send plain HTML over to the user. For example the Decision Drill[1] application performs a complete page load on every interaction, but the server is fast enough that at least with my internet connection, it feels to me like the corresponding React-based application would.

[1]: https://xkqr.org/decision/