Ways to find out unimplemented API methods needed by an app?

I'm using an app that depends on GMS. When using it with microG GmsCore instead, some features fail. I suspect that this is probably due to yet unimplemented API methods. If that suspicion is correct, then reporting the missing APIs to be implemented should be enough to make fixing the issue possible without the need of a microG developer to install the app, set it up, try to reproduce the error and finally find out what's wrong, right?

Since i couldn't find any hint about failing API calls via logcat (the app isn't crashing either), i have the following questions:

• What options do i have to determine the API calls made to microG by the affected app and find out which of them are only unimplemented stubs?
• Would it make sense to log every call to a stub API so it can be traced via logcat?
• Would a documentation on the implementation status of every existing API method make sense? (Or could anyone interested enough get that information by just studying the right files of microG source code?)

No file, test, or entry point is named. Begin by locating the relevant microG API implementations and stub handling, then determine whether the requested outcome is stub-call logging, an implementation-status document, or tracing guidance; done requires a maintainer-approved, scoped change with a verifiable way to identify missing methods.