As far as i know, we have to implement our own Subsystem. In my case, i need to add an extended Multiplayer System, which includes an Account-system where people can login to, a matchmaking System to let people randomly fight each other, and optionally some more features(like making it possible to collect/unlock cards by opening packs or something. But well this is not only related to multiplayer).
I am a beginner, so i am just learning by doing and some Video tutorials, which means that it will be hard for me to implement all of this on my own. Anyway i’ll work for it and maybe some day i’ll find someone who can help me or i even hire someone to do it 
I’ve asked for a discord server about the toolkit. Would be great to chat with other people using the toolkit