Patch driver (rtl8812au)

Install custom driver for rtl8812au chipset

Steps to get monitor mode working:

git clone https://github.com/astsam/rtl8812au
cd rtl8812au
git checkout v5.1.5
sudo make
sudo make install

Reboot
If you get build issues, be sure to have your headers installed:
sudo apt-get install linux-headers-$(uname -r)
or
sudo apt-get install linux-headers-amd64

To set the AWUS036ACH into monitor mode, you have to do it with iwconfig:
sudo ip link set wlan0 down
iwconfig wlan0 mode monitor
sudo ip link set wlan0 up

Now you can start airodump-ng:
airodump-ng wlan0