alt Hacker NewsI have given a try to data-star that is pretty similar to htmx, and it already had SSE support. (But I think it is a bit more complete solution to the problem - giving lightweight primitives for client-side interactivity)
I think it's (referring to both) a pretty nice framework, though it does require a bit of mental "undoing" if you have worked a lot with SPAs.
I've been playing around with making a little framework for building these server driven UIs in a way with a syntax more like SPAs. I originally was using datastar behind the scenes, but decided to just write my own version of it, much easier to work with.
https://github.com/StreamUI/hyperstar