The only difference between MicrosoftSdk and Standard projects is csproj file. Standard project is generated mostly automatically (except wildcards in ItemGroup nodes), while MicrosoftSdk csproj was created manually, inspired by Baseflow implementation of ExoPlayer Xamarin port. I think this approach is much better, since it makes csproj files much more readable and can support multiple target frameworks if needed. I guess there're also some other advantages as well.

So, main problems in Rider:

1. MicrosoftSdkBindingsLibrary\Additions\StateProvider.cs - everyting is red, Intellisense doesn't see files from obj\$(Configuration)\$(TargetFramework)\generated\src and obj\$(Configuration)\$(TargetFramework)\generated\enums.
2. StandardBindingsLibrary\Additions\StateProvider.cs - everyting is red, Intellisense doesn't see files from obj\$(Configuration)\generated\src and obj\$(Configuration)\generated\enums.
3. SampleApp\MainActivity.cs - same problem, Itellisense doesn't see generated files from the referenced project.
4. Other issue: Rider doesn't care what TargetFrameworkVersion is written in csproj file, it always picks 11.0 (R - API 30) as target API. Problem relates only to StandardBindingsLibrary project.

Compilation is successful for all projects.

Android Studio project is also included. You can compile it and change there something, csproj will pick a compiled aar automatically (there're conditions in csproj files which give such ability).