See the UX431FN UART driver on this page. The UART Driver for the Asus Zenbook 14 UX431FN is another Whiskey Lake UART device in the Asus product. Asus has over the years made use of the same hardware in many of their computers. This Whiskey Lake UART from Intel is one of them which has been used in many others such as the UART for ASUS ZenBook 14 UX431FA as well as the VivoBook Pro 15 N580GD notebook. You can find other UART driver for Asus listed on this website.
ASUS ZenBook 14 UX431FN UART Driver Win 10
You can see the list of files inside the zip file on this website. The UX431FN UART driver is listed below. You will note that there is an inf file which you will have to right-click on the inf file and then clicking on install. You also have the option of simply clicking on the install file which will install the Intel UART driver for you or you can use the device manager. Normally when you refresh it will ask you where the driver is and then you simply browse to where you extracted the zip file on your computer. Note again that this driver was released in May 2019 and is a Windows 10 64bit UART driver file.