I have a Mesh with 4 Deco M5 at home. There is one located at bed room which is far from main deco, so I used a network cable to improve performance from main deco to bedrom deco.

If its in router mode, ethernet backahaul doesnt take effect even if port is blinking. I`ve tried several ways to connect: direct port to port between main and bedroom APs and using a switch but it doesn`t any way, there is only a very weak wireless connection (because of distance and walls).

 In the other hand, if it`s in AP mode ethernet backhaul works inmediately regardless I use the switch or direct connection and performance is the best. I need to use it in router  mode coz I need to use parental control wich is not supported in AP mode.

Regards.