GNU/Linux Mint 19 ASUS USB-AC68 Wifi Driver Setup – Step-by-step Guide
Hi! The linked Tutorial shows you Step-by-Step How to Install ASUS USB-AC68 AC1900 Wireless 802.11ac Driver in Mint 19.x Tara/Tessa/Tina/Tricia LTS GNU/Linux Desktop.
And the Mint 19 ASUS USB-AC68 Setup is based on the Realtek rtl8814AU Chipset Driver Installation.
So the linked guide explain How to Download and Install the rtl8814AU Linux Driver.
Finally, in case to check your Adapter Chipset see: How to Check Wireless Device ID on GNU/Linux.
GNU/Linux Mint 19 ASUS USB-AC68 Wireless Driver Installation Guide