The Daemonbite project (https://github.com/MickGyver/DaemonBite-Retro-Controllers-USB https://github.com/MickGyver/DaemonBite-Retro-Controllers-US...) does esse

The Daemonbite project (https://github.com/MickGyver/DaemonBite-Retro-Controllers-USB https://github.com/MickGyver/DaemonBite-Retro-Controllers-US...) does essentially the same thing, but works like a normal USB controller from the perspective of the host. I've used one with a MiSTer FPGA setup and it's almost indistinguishable from a native SNES controller in terms of response. For my build, I cut a cheap controller extension cord in half, avoiding the need to actually modify the controller itself.