Unable to add DSL-68U to aimesh network as node

[Illuvattarr]

I want to add an ASUS DSL-68U with Merlin firmware as node to my existing aimesh network with 2 other asus devices (RT-AX82U), but cant get it to find any nodes. The DSL-68U is factory reset on merlin firmware.

I only set it up so that the first ethernet port is now a WAN port in order to add it as an aimesh node with cable setup like this (

). So ethernet cable is connected to WAN on the DSL-68U and to LAN on main ASUS. But searching for new Aimesh node is not working and doesn't find anything. Not through cable or wireless within 1 feet.

I'm not sure if this is necessary but I also tried removing the merlin firmware by flashing it through the Firmware Restoration tool in Rescue Mode (like this guide exactly; https://www.asus.com/support/faq/1000814/) but it always says this at 40% or 80%; Failed to upload the firmware file. transfer cancelled.

I tried both the newest firmware unzipped and the oldest one, but both fail.

How can I get this ASUS DSL-68U added as aimesh node??

 

[Ripshod]

It's been a while since I last tried this but when I did I had to flash the last asus firmware to the DSL-AC68U (via the webGUI) to get it to even work. I'm not sure it can even use wired backhaul as that'll just be reset as part of the pairing. Basically, wireless backhaul only.
Others may have a different experience though. Just my experience.