Show discovered HomeKit hubs
To see the HomeKit hubs Eero has discovered you need to go to the Home app right now. That wasn't obvious at all. I found it by accident in the end. On top of that the Home app only lists manufacturers, not specific hubs. I have two Ecobee thermostats but HomeKit only had one entry.
At minimum, right under the Eero HomeKit section where it shows all the enabled Eero ApPs, show where you can find this information in the Home application rather than have people either not know or have to look around like I did.