I work mostly proprietary projects, but one of my frameworks is open source:
https://zakadabar.io Please note that this one is about to retire and being replaced with my new one:
https://github.com/spxbhuhb/z2
That said, I programmed quite a few (25+) years before I settled on KMP for the last 4 or so, never looked back (used Java + React before).
When talking about browser development you might find integration with JavaScript libraries a bit of an overhead.
This doesn't matter for me as I avoid dependencies as much as possible, but most programmers like to build on them.
Basically you have access to all browser functions from Kotlin without doing anything, so there is nothing you can't do.