I have a MacBook with an Xbox One controller connected and can't get it to function. To set this up I used the Xbox 360 Controller Driver (https://github.com/360Controller/360Controller/) and it works property in the settings. However when I run FPV Freerider, it doesn't seem to "grab" the controller for the USB option but is grabbing some other device which doesn't register any behavior during calibration. I used USB Overdrive to find and disconnect everything that might behave like a controller (which was a speaker and a mouse), and still the FPV isn't grabbing the XBox controller. Using device monitor, there is a security chip that might seem to be a controller. So not knowing what FPV is binding too makes troubleshooting this impossible. If we cannot select from a list of controller choices, would it be possible to at least display the name or path to the controller that was selected?
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Not sure what the mystery controller might be. I use Unity's built in input manager for the controls, I don't think it can show the name of the controller it's actually reading. Also I'm not a Mac user myself so I'm not very knowledgeable when it comes to Mac specific questions. At least on Windows joysticks/controllers that are being detected usually shoes up as a generic HID device in the operating systems device manager. Perhaps you could try to temporarily disable the last thing that you suspect might show up as a controller (although I wouldn't really recommended it if it is indeed some kind of security chip...).
My guess is it's the xbox 360 controller driver that doesn't get picked up as a joystick in Unity's input manager. Did you try to connect the controller without any extra drivers first? (A lot of the time generic gamepads automatically connects as joysticks, at least on Windows).