It’s not passed to rust. it’s a pass through pointer which will be handed back to the caller(managed layer). It’s to hold state by the caller when dealing with the native ffi API in this case the managed layer delegates are referenced by it.
Both libraries are for mobile, so the .so is for android not linux.
Compiling the ffi libs on desktop should certainly be possible and simple enough. When it’s going to be coming out as part of the nuget package, I dont know yet. Once it is out, we’ll certainly be mentioning it in the Dev update. To cater for the full PCL 44 spec and a standalone package for .net, there might be other requirements that desktop platforms will also have to support like url manipulations between app and authenticator which can be achieved via the system_uri crate to keep it in sync with the other desktop apps, but yeh these are all things that is currently being worked on, so “sometime hopefully soon” is going to be my guess for now.