GNU/Linux Kali Realtek rtl8723AU Firmware Driver Setup – Step-by-step Guide
How to Install Realtek rtl8723AU WiFi/Bluetooth Driver Firmware on Kali GNU/Linux desktop – Step by step Tutorial.
Most noteworthy: the Driver may just be missing the Proprietary Firmware because thertl8723AU Module should be already provided by the Linux Kernel!

Installing Realtek rtl8723AU Wireless Driver on Kali GNU/Linux