I think what you want would be a bit of work, if you just want to have an electron like app you need to implement for each platform and use their native web framework (webkit on macOS, UWP on Windows and on Linux maybe embed in your library an web engine like webkit) then build a bridge or some kind of way to interact with the html/css.
If you use this approach your apps will be smaller on Windows and macOS but on Linux you will have almost the same overhead of electron, just b/c you need to embed the webkit/chromium on it.
May you start on Windows that will be easier b/c its well documented
On mac you need to check the framework documentation, but its just a documentation, maybe you need to find examples or tutorials on how to use it
And last Linux, I’ve no experience on embedding webkit or chromium.
The only thing that I don’t like about Kotlin Native its that you could only use with CLion and I don’t have any license to use it.
You can check this thread about the windows webview