Funny seeing this here with your comment, as I was exploring using ECharts for a project recently to work exactly with HTMX from a Clojure backend. I eventually settled on Chart.js as I found that for my use case, I wanted the charts to more easily fit their dynamically sized container, which isn’t quite as simple with ECharts and Vega. I also didn't need particularly complex plots. Nevertheless, this is a nice project! There remain some open challenges with web-based visualisation libraries more generally around responsive design and accessibility, but we’ve come a long way.