It's hard for me to give a blanket answer to this. I tend to mostly work on services that offer GraphQL APIs these days, and not so much on client side rendering. For APIs I stick with Go because it's what I'm most familiar with. But I'd also be happy to work on a Django or FastAPI service. Anything is fine really, as long as it's mostly boring technology.

If I had to create something that has a UI I'd just go with a bog standard server rendered multi page app, built using really boring technology as well. If you like Javascript and friends, go with Express. Nowadays you can run Typescript files directly and the built-in test runner is quite capable.

If a single page application makes sense, then go with vanilla React. For a highly interactive application that's potentially behind a log in anyway, you probably don't need React Server Components.