@Dauson 

I think OneMesh has not been designed to work this way.

Check out the information on this page:

https://www.tp-link.com/en/onemesh/

For your convenience here the most important part from the Q&A:

Q3: How do I set up a OneMesh™ network for different types of devices?

A3: You can use a OneMesh™ Wireless Router or Modem Router with several sets of Range Extenders or Powerline Adapters to create a OneMesh™ network. Be aware, you cannot create a OneMesh™ network between two routers.

@woozle 

Thanks, but it doesn't make sense.

Given two excellent products that support OneMesh technology and can't be connected?

I think this could be done smoothly as there are no technical hurdles.

I understand the business model, but somehow there is only a solution to it.

It's possible with two ARCHER AX73

First one mesh enabled for both. Secondly, WPS at the same time for both for the first configuration : IT WORKS !