summoned wrote @Alexandre., I am completely aware that this is doable and if I do it I'm sure that I will have internet connection in House 2. However, this experiment would not prove or disprove...

@Jepps Sorry, I misread you. Yes, you will need one more Deco M4.

@Jepps You said you have one M4 downstairs and another M4 upstairs. You can keep it that way. Is one Deco unit not enough upstairs?

@Jepps Deco mesh will not share WiFi with router. What you have now is two separate independent WiFi networks: one from router, another from Deco mesh. The right solution is to deactivate WiFi on the...

@Bruno74 Good. Let's focus on Vodafone router. From what you told me alredy, the slow speed you are getting might be from either speed testing device ("You are not testing it right") or from Internet...

@Bruno74 If you got 1500Mbps Internet link from your ISP, the router they supplied you with must support WiFi6 at least. With iPhone 15 Pro Max you should be able to get gigabit WiFi speeds from ISP...