We have used Kotlin/JS to make a web version of our Android mobile learning app ( Ustad Mobile). The web version is still pre-release. We also made a library to run Room databases on Kotlin/JS (using SQLite.js to use SQLite within a browser):
https://www.github.com/UstadMobile/door
Our current production bundle size (including react/JS, MUI, etc) is 2MB, which isn't ideal, but isn't the end of the world.