@HAL2000 Synology NAS DS220+ owner here. These are my NAS network configuration settings that do work. IPv6 is disabled - I suggest you do the same. NAS is connected on LAN 1. LAN 2 has self assigned...

@NoAngel Here is what I have. My Synology NAS DS220+ is wired directly to the router (it would be to Huawei EchoLife HG8045Q in your case). I run Deco mesh in AP mode, just like you. With that setup,...

@JGMH MFC J985DW printer description says it has Ethernet connectivity. Try connecting printer with Ethernet cable to one of Satellite Deco, to see if that works.

@kbs404 Also, here is how to use that feature when it appears in Deco app: How to select a preferred signal source on the Deco App

@kbs404 Deco M5 official firmware has the feature (Connection Preference) that allows to configure how Deco units connect to each other. M4 - does not. For that feature to be available in Deco app,...

@Koeke This TP-Link FAQ document should help: General questions about Ethernet Backhaul feature on your Deco