It took me a lot of time to figure this out and I thought I would share it with everyone. The driver provided for Linux by Ourlink may not work with the newer versions of Ubuntu. In this article, I am gonna explain how to install the driver and get it working on Ubuntu (I verified on the 20.04.2.0 LTS version).

Open the terminal and run these commands.

sudo apt-get update\nsudo apt install build-essential git dkms\n

Now, to download the driver, clone this respository. Maybe do this inside the Downloads directory.

cd ~/Downloads\ngit clone https://github.com/brektrou/rtl8821CU.git

Enter into the driver directory you just downloaded.

cd rtl8821CU

Make dkms-install.sh script executable by running this command.

chmod +x dkms-install.sh

Finally, it's time to install the driver by running this script.

sudo ./dkms-install.sh

Now, load this driver module into the Linux kernel so that the driver gets \"activated\".

sudo modprobe 8821cu

If you get an error saying something like modprobe error could not insert 8821cu. Operation not permitted, this might be because you cannot insert unsigned modules in the kernel while the Secure Boot (which is default in the new versions of Ubuntu) is enabled. We can use mokutil to check if this is the case and turn off the Secure Boot if so.

Install mokutil if it's not installed already.

sudo apt-get install mokutil

Check if the Secure Boot is ON.

mokutil --sb-state

This will most likely return SecureBoot enabled.

To disable the SecureBoot,

sudo mokutil --disable-validation

Provide your password when prompted. Set a password for the \"disable\" action you just requested and confirm that password. It will be required later.

Now, restart the computer.

reboot

On the boot blue screen (MOK Management),

• select “Change Secure Boot State”
• Enter the password as instructed/requested on the screen.
• Select Yes to disable Secure Boot in shim-signed and then hit Enter

Now, log in back to Ubuntu, open a terminal, and check if the secure boot state again.

mokutil --sb-state

It should return this, now.

SecureBoot enabled\nSecureBoot validation is disabled in shim

This means the secure boot is now disabled. You can, now, go ahead and run modprobe again

sudo modprobe 8821cu

The driver should now be active. Go to “Wifi Settings” to see if you have two tabs available, one for your native wifi adapter, another one for the new adapter (Eg. “Realtek Wifi”).

ENJOY!!!

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For reference:16.04 - Is it safe to disable Secure Boot? - Ask Ubuntu