OpenRetroPad

https://github.com/OpenRetroPad/OpenRetroPad
ESP32/Arduino Pro Micro adapter for various input and output output devices
Inputs: SNES/NES, Sega Genesis/Megadrive/Atari, Sega Saturn, Playstation (and PS2) Digital and Dual shock, Nintendo 64, Nintendo Gamecube, Nintendo Wii Nunchuck/Wii Classic/SNES+NES Mini
Outputs: bluetooth-hid gamepad, usb-hid gamepad, nintendo switch usb gamepad, wireless usb-hid gamepad
Not all boards are compatible with all inputs/outputs; ESP32 can only do BT, micro is radio or USB

This project is focused on adapters specifically and does not appear to have significant remapping support. The https://github.com/OpenRetroPad/OpenRetroPadHW page contains additional information.

Works directly with cables for PS1, PS2, 3DO, Master System, Genesis (Mega Drive), Saturn, Dreamcast, NES, SNES, N64, GameCube, Mini NES / SNES Classic, Wii / Wii U (GC and remote Ext ports), and Atari joystickopen hardware documentation. The designs are generally not designed to be reconfigurable and are designed to be permanent adapters from a particular input to a particular output.