default or selected kernelversion does not have config value CONFIG_R8712U.
Result is shown for kernelversion 6.9.9

RealTek RTL8712U (RTL8192SU) Wireless LAN NIC driver

modulename: r8712u.ko

configname: CONFIG_R8712U

Linux Kernel Configuration
└─>Device Drivers
└─>Staging drivers
└─>Wireless LAN
└─>RealTek RTL8712U (RTL8192SU) Wireless LAN NIC driver
In linux kernel since version 2.6.37 (release Date: 2011-01-04)  
This option adds the Realtek RTL8712 USB device such as the
D-Link DWA-130.

If built as a module, it will be called r8712u.

source code: