@fcadena72 

Try turning ofdma off

@fcadena72 

Not sure if AT&T is the same but Xfinity has different packages for different routers. I had this problem when I changed my router. I asked Xfinity to register it and by mistake they used a different package and I was plagued by the slow upload speed. After many ours tweaking it I saw that the package was wrong and asked Xfinity to update it and after a power cycle it fixed the upload speed. Maybe that's why the ATT router is performing better... just my 10 cents. Cheers

@speedmaster thanks will give that a try. Have a great weekend.

@Cawsie I was only able to find that setting under the wireless settings. None of my tests performed were Wireless.

@Sultanmsa I also get slow speeds. I am Attching screens from my older Orbi, and my new tp link ax6000. 

I have direct connection Fiber from local provider. QOS off and all setting per posts are correct and on the laatest firmware. 

TPLINK

ORBI 

@Sultanmsa Well, after some tests i can say that it is beyond the settings avaliable on the router, a firmware bug maybe, with google chrome my upload goes normal as you can see in the screenshot, but not only the edge chromium, but all other kinda of devices like mobiles and notebooks, even wired, thats the result in the second image, and it does not change enabling the ipv6 connection, hope u guys work on it to resolve, cause it would be a mess if a big company like tp link cant be able to resolve this issue after more than a year

Edit: i forgot to say that my upload in google chrome after some time goes down like half of the speed, without a reason.

I am posting what worked for me after spending several hours trying to solve this issue. Like others here I am on a high speed fibre connection (Telus Purefibre 1.5gbps down, 940mbps up). I was able to get full up and down speed connecting wired to the ONT. I followed a lot of the advice given with regards to changing the AX6000 QoS bandwidth settings manually to above what my ISP provides as well as changing some of the advanced settings on my adapter to match (2.5gbps full duplex or whatever is highest). Additionally, I removed all the energy saving stuff that windows and Realtek use with the adapter.

None of these things worked! I was stuck at 20-30mbps uploads still through a wired connection. At this point I got a little mad and researched a new router, but really - I like the features the AX6000 has (hence why I bought it!) and I can see no reason other than a stupid setting somewhere that is stopping me from achieving the upload speeds I'm paying for.

I began to systematically go through every single piece of hardware and software related to anything affecting my connection and this is what I found out.

My motherboard is a MAG Tomahawk x570 Wifi, it comes with a piece of software called MSI Dragon Center.

MSI Dragon Center has a module called LAN Manager. When you look in there, it has a lot of the same features that the TP-Link AX6000 purportedly has (the QoS that they won't let us turn off). I figured, why have 2 things basically doing the same job... since I can't disable the one I disabled MSI's LAN Manager.

This solved my problem, my upload speeds went from 20mbps to 900mbps using speedtest.net.

My next problem will be when I upgrade to 2.5gbps up/down internet now offered in my area and need to switch to a multi-gig switch with a wireless router setup as an access point for my wireless devices. A problem for another day! TP-Link, maybe think about adding an extra 2.5gbps socket on your next routers!

tldr; If you're using a MSI motherboard and have MSI Dragon Center installed, turn off the LAN Manager

@Cansol Great tip. I have an MSI motherboard and had to change my router for a Netgear one and since then no issues. Anyway, I still have my AX6000 and will test as soon as I have time and if confirmed the issue I will post it here.
Cheers and thanks
Speedmaster