Can I create an android, ios and web with the same codebase of kotlin

I have created an android app with kotlin and it is on-demand to make it available for Web-app and IOS as well. So I searched on Google to find a way to do that and I got something like Kotlin for multiplatform and after reading that I got a point that it is possible to create an IOS app too with the same codebase.

But I don't know that the same codebase can also work for the web app or not? Or the question can be that "Is it possible to make an app for all the 3 platforms with the same codebase?"

Or I should switch to Flutter? But if I switch to flutter then I have to start migrating it from scratch. Which would be so time consuming. But I have listened, that we have to write the code for once on flutter and run it anywhere. While with kotlin I have to change many things for different platforms?

Am I right? What would be a better approach for the long term?