[kerryritter]

I'm surprised no one has pointed out the value of Ionic Framework (https://www.ionicframework.com). I'm a huge, huge proponent of this. TypeScript is a great language (in my opinion), UI code-sharing is inherent, and Capacitor (https://capacitor.ionicframework.com/) is great for all the native work you need to do. Worth noting you can do this in Angular, React, Vue, or pure JS.

This won't suit your needs for processing-heavy apps (though can WebWorkers help), but will work well for many apps (https://csform.com/top-10-apps-built-with-ionic-framework/ for a "top 10" list for examples).

I noticed after submitting that you mentioned machine-learning. Any reason you can't offload that to a web API and take the load off the client?