How will this improve sound? Using Ethernet for an endpoint is already optimal (Rule 5.) Or are you concerned that all devices on a network “hear” every conversation? Surely using a switch will have the same effect as a single wire network (and give you a route for updates)?
Yes.
No. When using switch all devices on a network “hear” every conversation also. So it’s necessary to use another isolated local network for roon core and roon endpoint only.
In addition the use of switch leads to the appearance of additional boxes (switch, psu), interfaces and cables.
You’re mixing hubs with switches. So be it.
However in any local network there are periodic requests / broadcasts for all local network clients that interfere with the endpoint’s core task, namely, playback audio stream from Roon Core.