✔️ DO start with including a netstandard2.0 target.
Most general-purpose libraries should not need APIs outside of .NET Standard 2.0. .NET Standard 2.0 is supported by all modern platforms and is the recommended way to support multiple platforms with one target.
✔️ DO include a netstandard2.0 target if you require a netstandard1.x target.
All platforms supporting .NET Standard 2.0 will use the netstandard2.0 target and benefit from having a smaller package graph while older platforms will still work and fall back to using the netstandard1.x target.
It is not clear that SelfInitializingFakes would benefit from supporting netstandard2.1 at this point .
Split from #79
As @thomaslevesque notes, the Cross-platform targeting advice from Microsoft says
It is not clear that SelfInitializingFakes would benefit from supporting netstandard2.1 at this point .