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Lottie for Android, iOS, and React Native
Render After Effects animations natively on Android and iOS, Web, and React Native
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SurveyJS
Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.
gsap for animation. ThreeJs if you want to do some 3D and basic html canvas with js for games I like this guy's channel https://www.youtube.com/c/Frankslaboratory
Unity can export to WebGL/WASM, so that's one option if you're making some kind of heavy interactive experience and you don't mind waiting for it to load. For just animations there are tools like Lottie that can help. I think things are generally a lot more fragmented than they were in the Flash/Shockwave days though.