It's coming. Flexbox (and CSS Grid) are implemented in Taffy [0]. Multiline text rendering and layout are implemented in cosmic_text [1]. Dioxus linked here implements a component system with state management and reactivity. It's all quite new though (cosmic text was only released 2 months ago, and it's only gotten to "mostly feature complete" as of a few days ago) and it hasn't all been combined together into a complete framework yet.

[0] https://github.com/DioxusLabs/taffy [1] https://docs.rs/cosmic-text/latest/cosmic_text/