@Riley_S Thanks for your reply. I'm not sure I understand your suggestion to swap the 2nd and farthest 4th unit? 

The closest Deco satellite is about 10M (~32') away through three interior walls. The next Deco satellite is about 8M (~26') from the first satellite, through 1 exterior wall. (about 10M, through 3 interior and 1 exterior wall back to the main Deco.) The last Deco satellite is in an out building 18M (~60') through 2 uninsulated walls from the 2nd satellite. (about 23M (~75') through the six walls already mentioned to the main Deco unit)

All units are in a single story home. All three satellite units source their signal from the main X68 rather than the nearest satellite.

  @Riley_S Thanks for the reply.

All the satellite Decos show the main as the signal source and have not found an option to change that. I've currently moved the outbuilding Deco indoors, sitting next to the 2nd satellite (in my description above).

I'm currently working on getting wired ethernet backhaul, in hopes to improve the situation, but unfortunately getting wired ethernet to the outbuilding is cost prohibitive at this time. I'm installing a switch in my crawlspace on the other side of my house to get ethernet to the first two satellite Decos. 

I've hunted all through the app on my phone, as well as the web interface, and find no settings for "optomize" network. 

This is all rather disappointing as the entire upgrade was to get better internet in the out building. I've used Zyxel powerline adapters for a few years, and it's too slow. I purchased a set (3) Deco P9 units, and it worked for a day, showing the powerline as the backhaul channel, but stopped and never showed that again. I was hoping these X68 tri-band units would work.

  @Riley_S You are awesome with your quick replies. 

I've thought of killing the main for a while, good to know the others might continue to negotiate amongst themselves. The wired backhaul is a big project for me (under my house) and will hopefully get better results when that is finished. (might be several days)

Totally unrelated: If I pull up the Tp-link community forms, (not logged in) I can't find my posts (this thread). I log in and still can't find my posts. My profile shows that I have posts, but when I click on my posts in the side panel, it shows "no posts"  The only way I have been able to respond to you is by going back in my browsing history. Strange, eh?

  @Riley_S Thanks for the US/EN explanation. Makes sense...

As a proof of concept, I strung a spaghetti mess of Cat5e, coax, switches, and MoCA adapters through my house to test my set up as planned (when I can get all the work done under my house)  The speed improvement was remarkable. I put the Deco back into the out building, and it miraculously sourced the closest Deco (in my mudroom). Even with a "medium" signal to my chromebook in my workshop (2 uninsulated walls-20' (6M) away n another outbuilding) my speed went from 7down/8up on powerline to an astonishing 283down/151up. 

The out building Deco went back to source the main Deco as I was disconnecting and cleaning up all the trip hazards inside my home. But as soon as I reconnected the ethernet backhaul to the other 3 Decos, the out building went back to source the closest Deco. I'm pleased with the results. I do hope they include a firmware update to choose the source like on the M5. 

Thanks for all your help. Cheers!

  @smarkkham604 

Yes the Daisy chaining works.  

In my situation,  going from main then about 30 feet to my next Kitchen Deco then to the next garage Deco about 30 feet away from the Kitchen Deco. Ok, the only way I could get it to "Daisy chain" was to (sort of)  "Faraday" my Garage Deco. That is 2 say I wrapped my garage Deco with aluminum flashing material so ALL SIGNALS would be drastically reduced. But still have some signal "leakage". This way in order for this garage Deco 2 work it must pick up the weak signal of the Kitchen Deco and NOT the main Deco.  And LOW AND BEHOLD the signal 📶 was connected to the Kitchen Deco. I achieved a "Daisy chain". I almost fell out of me chair when I saw that. so obviously I went back to me garage Deco and unwrapped it from its "Faraday cage"  and the "Daisy Chain" is still funtional.  WHAT A HELL OF A WAY OF DOING THIS BUT IT WORKED. I hope in the near future Deco will rewritte the coding to allow you to choose what and where each Deco unit will receive it’s signal.  

  But YES!  ladies & Gentlemen, after a year of trying I have finally achieved a working mesh "Daisy Chain".

  I hope this helps you.  Happy 😄 New Year 2023.

 Dave C. Stout