@PierreTdC 

Of course there's a difference between two routers in Easymesh and two routers (main router and and router in AP mode).

In first case the SSID is the same for the two devices and they emitting one wireless network - that's the purpose of a mesh network.

In second case every router emits a different wireless network (even with the same SSID).

If both routers are in Easymesh the only way to use AX58 for a main router is to reset to factory defaults and configure as such.

If you want to join AX58 back to Easymesh of AX55 you have to reset AX58 to factory defaults and add to the AX55 Easymesh.

Setting AX58 in AP mode is quite different than setting AX58 in Easymesh. I alredy posted AP mode configuration guide.

Here's how to add AX58 in Easymesh to AX55.

Here's a guide for building Easymesh with an ethernet backhaul (if you use ethernet connection between AX55 and AX58).

Note: To use AX58 in an ethernet backhaul Easymesh it has to be HW v2 - you can check that on its bottom sticker.