Because HubProxy was removed in the Core version of the signal client, then the question arose, in fact, how to connect to, say, 5 hubs? Do each connection for each hub? What if there are 10 of them? Move all logic to one hub?
Unfortunately, in the new SignalR (Core) you will have to do everything through one hub, or put up with the fact that there will be many connections and buy more memory for redundant connections.
The author of SignalR (David Fowler) wrote that in the future they plan to implement a new transport that will not have this overhead, but now that's how it is. Ideally, you need to make it so that in the future it will be easy to divide them into the appropriate hubs and, when a new transport is brought up, go. Answer on github