frank26080115 made a USB adapter for a USB Wii Classic Controller:
This project will show you how to create a real USB game pad using a Wii Classic Controller. The Instructable (full step by step instructions) is here
Once the adapter is working, the Wii Classic Controller registers as a standard HID gamepad on any PC. Forum members have reported using it with Steam titles, retro emulators, casino apps that support controller input, and various browser-based games. The analog sticks and trigger buttons map cleanly, making it a surprisingly versatile budget controller.
A demonstration video is here
Via the forum.