@beve 

I tested that with my M5. M5 connected through powerline adapter reports Ethernet connection and runs just fine.

Note the following:

1) Internet speed of devices connected to that M5 will be (obviously) limited by the speed on powerline adapters. You must have good electric wiring without much interference to get acceptable results.

2) Not every powerline adapter is compatible with Deco backhaul protocol. If you get one that is not, M5 will keep reporting WiFi backhaul, even if connected to powerline adapter. For some reason, adapters with just one Ethernet port have more chance to be complatible with Deco than adapters with 2 or more Ethernet ports.

If it helps, the one I have and confirmed working is ZyXEL PLA5215. It is outdated model, but still can be found for purchase.

@Alexandre. 

Thanks for your quick response. I will try it out with a few plc's.