Cross-Platform (Including Web) GUI Libs

I'm developing a prototype data-scientist-oriented IDE soon. I've done a fair amount of research on cross-platfrom GUI frameworks, especially ones which can be compiled to wasm/deployed-to-browser. But it's hard to know what one might have missed.

So I thought it's worth having HN share its collective wisdom on this question. Across any language, platform, framework (etc.) -- what is the best cross-platform GUI toolkit?

(My thinking at the moment leads me to egui, perhaps taking rerun.io as a guide, as I may also want to integrate a game engine.)

However, open question.