Your best bet is the Google release notes:
https://developers.google.com/android/guides/releasesOur packages use the same version numbers as them, except we add a 1 in front of them.
So for example, the NuGet package https://www.nuget.org/packages/Xamarin.Firebase.Crashlytics is versioned 118.0.1, which means it corresponds to the 18.0.1 Google release.
Answered by jpobst / Jonathan Pobst here - https://github.com/xamarin/GooglePlayServicesComponents/issues/486#issuecomment-869877496