@givemeatip 

Here is a link to a beta driver for the Archer T3U/T4U, you first need to uninstall the driver on the computer then run this drivers setup:

https://static.tp-link.com/2019/201911/20191128/Archer%20T3U_beta_U2_U3_5G%20unstable%20issue_1030.22.0202.2018.zip

The driver was mean to resolve 5G stabilization issues, but you can see if it helps with speeds. If not, you can still try other USB ports and also another computer to see if the computer is the bottleneck and not the device itself.

@Tony 

Hello, I uninstalled the driver/device, extracted your zip file to a folder and tried to run it. But I keep getting a "NSIS Error" message in a box that says "Error launching installer" when I try to open the Autorun.exe and the Setup.exe of the other folder of the extracted files. So there is no way to install this driver you directed me to install. Please help!

@Tony 

Hello I managed to run the installer by renaming the folder. But it didn't detect my adapter.

@givemeatip 

What you can try is to install the drivers manually, reference this: https://www.tp-link.com/us/support/faq/920/

Go into the "plugins" folder rather than the setup.exe, then select "driver files" > "driver" > Windows 10 64-bit, select the .inf file

@Tony 

Hello I installed the driver manually as instructed. It didn't solve any problem and the speed even lowered a bit.
Following the instructions to install drivers manually, I also managed to install the driver recommended in that other thread - https://community.tp-link.com/en/home/forum/topic/204682 - same results, didn't solve the problem and the speed even lowered a bit.

I returned to the driver Windows 10 version 1909 installs automatically. Please, fix this. Thank you. 

@givemeatip 

If you have another computer, take the T4U to that and see if you see the same thing as the desired computer may be the bottleneck.

@Tony 

Hello! I tested the product in my father's HP notebook which has an older Windows 10 version (1803) and the TP-Link Archer T4U worked perfectly, even the latest official driver from the TP-Link website installed normally. It reached very high speeds (almost 300 Mbps, which is what my ISP offers to me). And I'm not even sure that the USB port of that notebook is 3.0.

Now I don't know if the cause of my problems are the USB ports of the Dell notebook running Windows 10 version 1909 or if the cause of my problems is the Windows 10 version 1909. How can we clarify this? Is there a possible fix?

@givemeatip 

You could try rebooting the computer in safe mode to see if the issue is software related that exists on the computer reducing the speed. If the speed still is slow, see if there are new USB drivers available for the computer or any new updates for the computer.

givemeatip wrote

So, I'm having problems with this adapter TP-Link Archer T4U(US) v3.20 since it came for me. First the CD didn't recognize the adapter. The latest v3 US driver on the TP-Link website also didn't recognize the adapter. But then I noticed that Windows 10 had automatically recognized it. And so I began to use it.

I noticed that it's faster than the network adapter of my notebook, however, I noticed some problems:
- Windows 10 says it is not recognized as a USB 3.0 device (and it is connected to a USB 3.0 port here, the blue one!) - same problem as described here: https://community.tp-link.com/en/home/forum/topic/204682 

- Speeds don't go faster than about 125 Megas. I can hit 300 megas easily with an iPhone and a Galaxy S7 with the 5Ghz wireless network of the Huawei HG8245Q2 I'm using for the test. Tests were done with the Huawei very close.

- Wireless association speed seems OK: 866,7 Mbps
- Driver version is 1030.27.425.2018 (as I explained, Windows 10 automatically recognized it).
- I tested with disabled antivirus and other softwares - same results

- Running Microsoft Windows 10 Pro x64 latest official build (1909) with all updates on a Dell Inspiron 14R 5421 with i7.

@givemeatip 

It certainly seems to be evident that T4U usb 3 port is faulty or no connection is established with the usb 3 connectors of PC in spite of being connected to usb 3.... Its happening to me also... T4U usb 3 port is blocked somehow by tplink.. So port is getting connected by usb 2 mode. You should investigate why it is not getting connected by USB3 mode... The answer is simple... Usb3 connection is blocked in archer T4U. Now the question is whether TPlink will enable it via Dongle firmware update or not? Note this is not the Windows software, it is the firmware of the T4U hardware that needs to be fixed... If the internal connections of T4U's USB3 connectors are cut off during manufacture, then no firmware can correct this fault...

 So if T4U gets truly connected in usb3 mode in future then we all will get at least 100MB to 108MB per sec of transfer speed (equivalent to at least 800Mbps at 5GHz ac mode)... I am not talking about internet speed.. because if your internet speed is 400Mbps you will get 400Mbps, if your internet speed is 1Gbps you will get 866.7 Mbps....which is equivalent to at least 100 to 108 MB per sec..

TP Link should state that T4U v 3.2 works only in usb2 mode as of now. Or selling refurbished non usb3 products but labelled as Usb3.

This is the 1st so called usb3 device that never connects as usb3 mode in usb3 port... Extremely strange !

Its utterly funny that adapter connects to 5Ghz at 867.7Mbps , yet the true connection speed is around 250Mbps max via usb2 mode.

After investigating a bit I came to the conclusion that TP-Link Archer T4U 3.20 has a problem (maybe in the driver), its speed is limited to USB 2.0 High Speed, it isn't recognized as a USB 3.0 device even when connected to a USB 3.0 port.