Hi, I am very new to the linux environment and have just installed manjaro today. I had previously been using Ubuntu 20.04. I need a complete guide on the installation of drivers for the USB wifi card tp link Archer 600 T2U plus.
Welcome to the forum! 
Please paste the output of the following, highlight it and use the Preformatted text </> buttton:
inxi -Nazy
Sure!
Network:
Device-1: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet
vendor: Gigabyte driver: r8169 v: kernel port: f000 bus ID: 04:00.0
chip ID: 10ec:8168
Device-2: Samsung GT-I9070 (network tethering USB debugging enabled)
type: USB driver: rndis_host bus ID: 3-4:3 chip ID: 04e8:6864
serial: <filter>
Did you have the TPLink adapter connected when you ran the command? It’s not showing up.
Yes, it was connected via USB.
output for lsusb:
Bus 006 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 005 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 004 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 003 Device 003: ID 04e8:6864 Samsung Electronics Co., Ltd GT-I9070 (network tethering, USB debugging enabled)
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
Bus 001 Device 004: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)
Bus 001 Device 003: ID 0461:4d81 Primax Electronics, Ltd Dell N889 Optical Mouse
Bus 001 Device 005: ID 2357:0120 TP-Link Archer T2U PLUS [RTL8821AU]
Bus 001 Device 002: ID 046d:c52b Logitech, Inc. Unifying Receiver
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hubThere it is. You’ll need rtl8821au-dkms-git from the AUR (Arch User Repository) along with the Linux kernel headers the match the kernel you have installed. For instance, if you have 5.10 installed, you’ll want linux510-headers.
Can you please provide a step by step instruction on how to do it. I have no idea how to use AUR or install Kernel headers.
Check out the wiki link in my post about using the AUR.
What kernel do you have installed? You can check with:
uname -r
Output for uname -r:
5.9.16-1-MANJAROCheck out the wiki link in my post about using the AUR.
How can I do that? I’m sorry if I’m asking really silly questions but I am a total newbie here.
Just so you know, 5.9 is EOL (End Of Life). It stopped receiving updates over a month ago. The current stable kernel is 5.10. There is also the LTS (Long Term Support) kernel, 5.4. 5.10 will become the next LTS kernel once 5.11 is released next month. You can see the current status on kernel.org. To install a different kernel open Manjaro Settings Manager and click on Kernel.
Click the link 
Thanks!
I am installing 5.10 right now. Once I am done with that, how can I install the kernel headers?
output for uname -r now:
5.10.7-3-MANJARO
Like you would anything else, from Add / Remove Software. I already mentioned how to determine which version you need. 
Thanks! I am installing kernel headers right now. I’ll post a reply once I get my WiFi card working perfectly!
Hey, I’m getting an error stating:
Unable to install module rtl8821au/5.1.5.r83.g3a44070 for kernel 5.9.16-1-MANJARO: Missing kernel headers.
What am I missing here…
If you want to keep 5.9 installed, you’ll also need linux59-headers.
Also, to use a new or updated kernel / kernel module (like the driver you’re installing), you’ll need to reboot after installation.
I don’t want to, isn’t my kernel version 5.10 now…?
You’ll have to reboot in order to remove 5.9 since you’re still running it.
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I’m sorry, I realized the mistake myself. I did reboot after the kernel installation but I did not reboot after updating my kernel headers,