You can use this repository which uses the Maplibre SDK.
Before you start here, it might be simpler to use the Maplibre SDK directly in your app. See this PR for a basic demo app.
Or have a look into this end user application that comes with all features including speed and max speed information, automatic re-routing, quick hint for a second (chained) instruction, on-path arrow for the next turn and via point handling:
This app provides a capacitor plugin, but the code can be used as a start for a kotlin multiplatform integration without any capacitor dependency. And as the latest Maplibre Navigation SDK is KMP-ready too this code can be easily ported to iOS.
Furthermore you can use GraphHopper with the ferrostar SDK. See this PR.