Curious, has anyone been able to make true multi platform compose with one codebase deployed too Web, iOS, Android, Windows, Mac, Linux? Is it theoretical possible or practical? Is it closer once we get Wasm Kotlin?

Theoretically yes, there are a couple of samples doing that already. Now, practical for a big enterprise type of App, at this point I would say no. Web and iOS still lack support in some basic components.

Many years ago, I spent 20 years using Smalltalk to try and realize the "cross platform" dream, just between MacOS/Windows/X11. You can do trivial stuff easy, and in the end, it only goes so far. I concluded it's not really possible. The Java guys then tried. And had similar results. As have many other toolkits with varying degress of success. I've done Flutter, and again, same conclusion. I won't say that someone won't pull it off someday, and I won't begrudge their success--I'll even cheer them on--but my experience won't allow me to personally bet "this time will be the time finally". but i'm happy to be proven wrong.

It depends on the difficulty of the project, the more complex the less likely to fit. But I see it feasible in many types of projects. There are plenty of react native Apps in production. Flutter perhaps not so much, because in my opinion, they did not target an already popular language. But I do see a decent market for cross platform frameworks.

I was thinking only compose with adaptive layout. Not sure if I would try, maybe for fun iOS/Android/Web. Also it has to be good performance, no compromising and good compose code. Never seen any do this successfully yet. I would also guess it depends what refer as success. Doing if iOS elseif Windows else this, then no same code.