I've used VLANs in routers that could do it. That worked great without any special setup. Surprisingly it was Centurylinks' rejigged FW for their supplied routers. Now I'm doing Out of Range IPAs and IPA Reservations. I have Gigabit Fiber with PPPoE and I think it would take 3 routers to do what suggest, since the ONT is a dumb converter. I'm in the process of going Fiber Direct Ubiquiti. Been waiting on their new gear to come out and then I can do all kinds of killer things. Even though my current WiFi6 Mesh system is great.
I pulled the 2 Solo Hubs the Training Tech installed when they installed the two H3s and replaced them with a Duo ($9 from Walmart) and cleaned up all that long ago. There should be pictures lying around here someplace.
Sorry to be late to the party, however I thought I would give my experiences as well in regards to this.
I've had my H3 using the TOP RJ45 port since 2015.
After a short period of time with using a non managed 24 port home LAN switch, and since I fiddle around with routers and such which other home users complained about, I changed the Switch configuration around a bit and put my H3 and two Joeys on there own separate switch segment behind the host router. So there connection won't be interrupted by anything I do on the main home switch network. Of course, if I do something at the host router level, then I do this when everyone is in bed or out of the house.
So the Hopper system is connected to a non managed Netgear GS108 coming of the back of the host router. I have another two lines that runs from this 108 switch to the master bedroom were 1 Joey is and then a 2nd line from the 108 switch to the living room down stairs that services the Joey in the living room. There is a Netgear GS 105 switch at these to locations for the Joeys to connect to and other wired devices when needed.
I have had this configuration for over the past few years and haven't seen any problems with it.
Anytime I change out the host router I do power cycle the H3 and Joeys to ensure they get good IP addressing and avoid any IP address collisions.
I've also tested D-Link and HP Procurve branded switches as well.
Other then that, this configuration works and works well.