JetBrain's Jetpack Compose for Desktop is an open source project being developed in collaboration with Google’s Jetpack Compose, intended to simplify and accelerates UI development for desktop applications, and allow extensive UI code sharing between Android and desktop applications. It's first milestone release is now available.
Is a 100% shared codebase between different platforms a futile dream? Many have tried to cross boundaries with a framework that can bridge multiple platforms, that is write your code once and let it run seamlessly on macOS, Linux, Windows, and iOS.
But, if even Microsoft can't unify the UI framework of its Windows platform, what can you expect from attempting to go across platforms?