My last experiment was with bulma css and vanilla javascript (typescript) with web components for components that needed custom/complex interactions. Nice thing with this approach is that you can "just" render the web components with the backend's template engine as if those were your normal html tags. Because of typescript, a build step was required. For this I used esbuild (esbuild itself didn't do the type checking so I ran tsc with --noEmit and --watch next to it).

Didn't get that far with that project to see how it works when the code base scales. I would probably pick the same setup for my next greenfield project.