Problem with TP-Link TL-WN823N

I was going through the same problem. Here is how to solve it, even though it doesn't solve the nameless problem:

If you have wired internet available to your problem PC

1. Follow this answer, which adds Pilot6's rtlwifi PPA to your sistem and installs the required rtl8192eu-dkms package.

If you have no internet access in your computer

1. Find another computer with internet access to download the rtl8192eu-dkms package manually.
2. Access https://launchpad.net/~hanipouspilot/+archive/ubuntu/rtlwifi
3. Click on "View package details"
4. Filter your Ubuntu codename (16.04 LTS is Xenial).
5. Click on the triangle to open more options of "rtl8192eu-dkms - 4.4"
6. Download rtl8192eu-dkms_4.4_all.deb.
7. Transfer this file to your target PC
8. Install the file on your target PC, either through the Software Center or the Terminal (by issuing dpkg -i <filename> in the appropriate folder).
9. Re-plug your dongle.

Here's a screenshot to better show the location of the download link:

Source of image: https://launchpad.net/~hanipouspilot/+archive/ubuntu/rtlwifi/+packages?field.name_filter=&field.status_filter=published&field.series_filter=xenial

The driver for this dongle can be installed by

sudo add-apt-repository ppa:hanipouspilot/rtlwifi
sudo apt update
sudo apt install rtl8192eu-dkms