I am using this set of class libraries in three projects now. Obeying the Rule of Three I am generalizing most of it now. You should be able to reference these libraries from .net4.6, .net core 1.0, Xamarin and UWP. The more abstract the library the lower the required .NET Standard gets.
| Abstraction | .Net Standard | NuGet |
|---|---|---|
| Backend.Fx | 1.3 |  |
| Environment | .Net Standard | NuGet |
|---|---|---|
| Backend.Fx.AspNetCore | 2.0 |  |
| Backend.Fx.AspNetCore.Mvc | 2.0 |  |
| Backend.Fx.NetCore | 1.3 |  |
You get vendor locked to a set of abstractions, like my DDD building blocks and some architecture patterns defined as interfaces
| Vendor | Library | .NET Standard | NuGet |
|---|---|---|---|
| Entity Framework Core 2.1 as persistence mechanism | Backend.Fx.EfCorePersistence | 2.0 |  |
| InMemory Persistence implementation | Backend.Fx.InMemoryPersistence | 1.3 |  |
| NLog logging | Backend.Fx.NLogLogging | 1.6 |  |
| RabbitMq Message Bus | Backend.Fx.RabbitMq | 1.5 |  |
| Simple Injector as DI container | Backend.Fx.SimpleInjectorDependencyInjection | 1.3 |  |