Incompatible USB and BLE Devices

Known Offenders

Non-modern-style gamepads targeting emulation of old game consoles often have strange button mappings. You'll find these in your drawer of buyers remorse and wishful thinking. Submit a patch to pad.c if you want it working.
All USB XInput devices will not work. I wrote a driver, but TinyUSB is hot garbage on the Pi Pico so it's disabled. Check your manual, many devices can be put in DInput mode instead.
Nintendo Switch Pro Controller - These are supposed to be plain HID but mine doesn't even work on Windows.
Some USB hubs crash the USB stack but I can't tell you which ones because over a dozen assholes asked for free support and didn't bother to tell us which hub didn't work after they bought a new hub which fixed the problem.

Any gamepad that looks like it belongs on XBox, Windows or PlayStation is a recommended gamepad.