From sgcWebSockets .NET 4.5.4, MacOS 64 bits is supported, so now you can compile Visual Studio Mac Applications for Mac OS 64 bits.
The components supported by MacOS are the same that for Windows, so you can build multi-platform applications using sgcWebSockets .NET library.
Find below a video which shows how install sgcWebSockets .NET package on Visual Studio for Mac and how create a simple websocket client.