@Evil1nside 

I have AX55 routers here but the EasyMesh setup procedure is the same.  If you do a factory reset of the satellite router, it should default to using a Dynamic IP on its WAN port.  During the EasyMesh setup, the main router will assign an IP to the satellite router using DHCP and, for now, it is not possible to assign a static IP to the satellite router when using EasyMesh.  Perhaps that may be fixed in a future firmware update.  In my case, I use Address Reservation on the main router to assign IPs to the satellite router and any range extenders.

You should try tp place the routers (temporarily) near each other to initially set up EasyMesh.  After they mesh wirelessly, you can make a cable connection between the routers to test that ethernet backhaul is working.  Finally, you can then relocate the satellite router to its desired location.

  @jra11500 
I tried this already and it did not work.
Probably a FW update is needed on either side(AX73 and/or AX53) but we will need an official word for this.
Also this further proves that the official setup guide is not really relevant, since it asks for the satellite router to be reset to factory defaults(preferably the main router too) and connected to each other LAN to LAN on both ends, and not LAN to WAN.

If you DO connect them LAN(on the main) to WAN(on the satellite) then Ethernet backhaul is not working, but instead, an EasyMesh is created via WiFi, and if you then switch to the LAN(on the satellite) then EasyMesh is NOT recreated in Ethernet mode, but instead, the whole local network goes down because of IP conflict between both routers.
And trying to access either is not possible, through web GUI, or even the Teather app.

Something is definitely rotten here, and I'm not sure if this could be a design flow, a FW update is needed on either of the 2 routers, or a much more advanced guide is needed.

Either way, I'm happy with what I currently have, and how the network is build and working, I simply wanted to give this a try, but instead, it gave me a huge headache, so I addressed it :)  

  @Evil1nside 

Hi,

In case your AX53 is hardware version V1, then you will need to install the beta firmware linked to in the table of the first post of this thread. https://community.tp-link.com/en/home/forum/topic/593722

  @woozle 
My AX53 is V1, but from what I can see, I'm already running a higher build ID version then the public beta firmware.

Beta: 1.2.4 Build 20240206
My Version: 1.2.4 Build 20240509

Do we know If this feature is only available in THIS particular beta, thus not yet part of the live(not beta) firmware?
Are we sure that this has not already been made available to the live version that I have?
Judging by the build version, this beta is from February this year, and mine is from May, which is a good 3 months newer then the beta, and it will be really, really odd if it isn't already included.
 

  @Evil1nside 

I see that there may be a problem with your router's firmware version but I can not comment on that.  What I will say here is that my satellite AX55 running EasyMesh is connected to the main router using its WAN port.  The router is in a "hard-to-reach" location and I confirmed this yesterday.  It really makes no difference which one you use (LAN or WAN) once the network is set up (at least with the AX55).

On another point... Once you reset the satellite router to factory defaults, do not log in to it or do any other actions, otherwise the EasyMesh setup might not work.

  @jra11500 
Thanks for the clarifications, it's much clearer now.
I guess I'll just wait for the live version of this firmware to be released which will include this feature outside beta, because as I said, I'm pretty happy of how things work currently regardless.
My AX53 is also in a hard to reach place from the main, but they are both connected via Ethernet(LAN on the main, WAN on the secondary) while the secondary is set into a repeater mode, instead of a router mode, and this way I'm only using the main DHCP as a gateway to the rest of the local network.
Things work flawlessly as they are, I was simply hoping to minimize the WiFi interference a bit, because currently both main and secondary has their own separate WiFi names and everything, which is also not optimal, but not terrible either. I can live with the way it is currently :)

Thanks once again!

  @Evil1nside 

Just a short comment...  It is perfectly OK to assign the same SSIDs to the main router and the access point router.  Roaming isn't perfect but in most cases your devices will connect to the strongest signal.  If interference is not too bad in your area, put the access point on different channels from the main router but with the same SSIDs.  This will allow you to determine whether your device is connected to the main router or the access point by looking at the channel information of your device's connection.

  @jra11500 
Interfearance is bad in my area, really, really bad. 
There are like 20 other networks, and scanning the channels I can see that basically no channel is without any sort of interfearance by other networks, there simply few that are a bit less overloaded then the others, to put it this way :)