@satrapal For Connection Preference feature to work and be available in Deco app, all Deco units in Deco mesh must have firmware that supports it. Your new M4R(EU) Ver.2.0, FW: 1.6.2 has firmware...

@SwatKat Yes, you can do that without any issues.

@Raunar Try factory reset of that Deco, follow Method 2 from this document: https://www.tp-link.com/en/support/faq/1457/

@malibu66 TP-Link Deco enforces private IP address ranges for LAN: 10.0.0.0 to 10.255.255.255 172.16.0.0 to 172.31.255.255 192.168.0.0 to 192.168.255.255 -------------------- There is no full WebIU...

@MediuM You should return this product. Deco E4 has 100Mbps Ethernet ports, which means it won't deliver faster than 100Mbps Internet connection speed. If you plan to buy different WiFi mesh set...

@Martijn43 In case you haven't tried it yet: yes, it will work. You can connect multiple Satellite Deco directly to Main Deco, if Main Deco has enough Ethernet ports.