I’m not sure what you mean by the controller. The thermostat is connected to the COVR network. My smartphone is connected to the COVR network. The AppleTV that’s the central HomeKit hub is connected to the COVR network. When I try to add the thermostat to HomeKit from within the Ecobee smartphone app, it doesn’t find the thermostat. I’ve been able to add a Schlage smart lock and a Lutron hub.
Does the COVR system use 5GHz only? If it uses 2.4 and 5, I’m not sure how adding a 2.4 WiFi router with he same SSID/password would let the Ecobee connect, since the Ecobee is already connected? If the problem is my smartphone connecting over 5GHz, would an additional 2.4Ghz WiFI router force the smartphone to use that router?