Have been searching why my wifi network became really slow and came to the conclusion it has something to do with the selected channel the deco chooses on 5Ghz.

Switching to 2.4Ghz my download speed went to 8MB/s, on 5Ghzv I can only get around 1.5MB/s.

Isn't the whole point of a mesh system to get fast and stable speeds??

Its time to boycott Deco and TPLink really. I bought 3 of them and they keep connecting stupidly all over the wrong channels and use a weak backhaul when there is a better ome available. 

All their CS does is stalls. I really want to return the 3 deco m9+ i bought because it is utter trash. It doesnt take 4 years to give simple functionality to choose bands and force decos to connect to the right ones. 

  @crashtec the CS stall is real!
 

It took them over a year to finally spend time with me to review my issue. They scheduled a time to remotely log in and simultaneously live chat with me. Given the time zone difference I had to schedule for the start of their day, which was 10pm my time. They took hours, I was up until 2am working with them. Their communication was poor at best during this time, more stalling, delaying, taking other calls. I do think they just wanted me to disconnect, but I stayed with it!
 

Finally they agreed there was a major issue and recommended replacing my units, all 3 Deco M9+. Conveniently, I was 3 days past warranty (apparently 2 years from manufacture date, which was provided to them when the initial support case was opened) and there was nothing they could do. They kindly recommended I buy their new technology and offered me a 10% discount. 

I truly feelt that my devices should have been replaced, given the issue and ask for support was more than 12 months old. TPLink intentionally delayed support in my opinion.

  @David-TP 

I know this thread is old but as it has been 2 years and there still isn't an option, I guess the engineers decided against it (or perhaps I just don't know how). I thought I would offer a suggestion for WHY we might want some control over the channels. I recently found out that my wireless headset occasionally conflicts with the channel chosen by my Deco M9.

Since my headset never changes channels I think an alternative solution would be to block certain channels from Deco, this would still allow it to change channels based on the need to make everything seamless but also allow us to reserve certain channels for other devices.

  @David-TP Is there still no news on this?  I require this feature.  I had preordered the new be95, but cancelled it once I read through this thread and empty promises.  If you're not going to do it, it would be better to just say so.

  @David-TP 

I ended up reading this post because I too was looking to manually select an alternative 2.4GHz channel for my whole Deco P9 mesh system.  Some of what you have said in your previous response may be true, but for TP-Link not to provide configuration options to customers who have the necessary technical skills to assess and make changes for themselves, when those same customers are experiencing performance or unreliability issues associated with the settings that the Deco P9 system has chosen for itself (as in my case), is simply not satisfactory.  I would urge your developers to provide greater accessibility to the configuration settings of this product.

  @David-TP 

I really would like to change channels as my neighbour has an Orbi and he can't change channels either.....

Its worse than described so far. 

The M5 is not only taking up almost all channels (3-11) of the 2.4Ghz band but also extremely loud and causing interference with both neighbors.

The neighbors now bought new wifi gear with maximum output to overshoot my M5's interference with their networks.

There is no need to use so much bandwidth for old 2.4Ghz legacy devices (wifi printers, some IoT devices, etc). They need the extended reach, not speed.

Just 20Mhz is enough and we could all stick to the channel 1,6,11 principle and work it out.

Besides setting channels and bandwidth, there should also be a way to set the transmit power (dBm).