Radio stations are currently not supported by the MusicKit SDK for Android. The SDK has not been updated for years now. It lacks pretty big features of Apple Music
Please file an enhancement request using the Feedback Assistant so that your request can be seen by the appropriate decision makers. If you file the request, please post the Feedback number here so we can make sure it gets routed to the right team.
Please note that filing an enhancement request does not guarantee Apple will add any requested functionality to Apple products in the future. However, with that said, filing an enhancement request is a good way to get your ideas in front of the folks who make decisions about that sort of thing.
If you're not familiar with how to file enhancement requests, take a look at Bug Reporting: How and Why?