The Steamworks C# implementations I found that were compatible with Unity have worked for a long time. But I hate them all. For a number of different reasons.
* They're not C#, they're just a collection of functions.
* They're not up to date.
* They require a 3rd party native dll.
* They can't be compiled into a standalone dll (in Unity).
* They have a license.
C# is meant to make things easier. So lets try to wrap it up in a way that makes it all easier.
Yeah this works under Unity. That's half the point of it.
There's another repo with an example project with it working in Unity. You can find it [here](https://github.com/Facepunch/Facepunch.Steamworks.Unity/blob/master/Assets/Scripts/SteamTest.cs).
The TLDR is before you create the Client or the Server, call this to let Facepunch.Steamworks know which platform we're on - because it can't tell the difference between osx and linux by itself.