GNU/Linux Ubuntu 18.04 Realtek rtl8723be Driver Installation Guide
Hi! The linked Tutorial shows you Step-by-Step How to Install Realtek rtl8723be Wireless Driver for Ubuntu 18.04 Bionic LTS GNU/Linux.
The Realtek rtl8723be Ubuntu 18.04 Driver should be already bundled into the Linux Kernel.
But if needed as a replacement see the Realtek rtl8821CE/rtl8192CE Driver Setup.
Installing Realtek rtl8723BE Driver for Ubuntu