@GoodWifiForEver This is unusual, indeed. Please re-run speed test, but with the following: Use Ookla speedtest app. Verify it picks same speed test servers at each run; Power off Satellite Deco...

@yoyolele Every Satellite Deco that has Ethernet port can use it for Ethernet backhaul.

@aggivatedMAN With Deco, you can achieve that by utilizing Guest Network:

@smigs 85-90 Mbps sounds just right if your Satellite Deco uses WiFi backhaul. Check what it says under Signal Source for Satellite Deco in Deco app: just connecting Satellite Deco to Ethernet cable...

@Livento You said "2 units separated by about 40 feet on alternate ends of the house." It is possible that at least some of issues are because Satellite Deco is too far from Main Deco. If your Main...

@alexc7 I am not sure why did you have so many struggles. With working router, such as THG3000, initial Deco setup should have been straightforward, just like it is shown here:...