Second hat not being shown in Linux

Description of Issue

Hat0 shows and behaves as expected, but Hat1 does not interact with the system at all - on Linux Kernel 5.4 and 5.12. Hat0+Hat1 both show up in Windows 10 and Linux kernel 4.15.

I've looked at the /dev/event/eventX and /dev/input/jsX devices with evtest, jstest, and a straight cat on the device output. One 4.15, it shows HAT1X (event 18) and HAT1Y (event 19) as expected, in 5.4+ it does not show at all and no activity is registered on the cat output.

Technical Details

Board: SparkFun Pro Micro
Host OS:
- Not working correctly: kernel 5.4 (Linux Mint 20.1), kernel 5.12 (Linux Mint 20.1, XanMod stable)
- Working correctly: Windows 10, kernel 4.15 (Kubuntu 18.04)
Arduino IDE 1.8.15

Sketch File that Reproduces Issue

This is a stripped down sketch that doesn't use actual hardware, to avoid any potential hardware issues:

#include <Joystick.h>

Joystick_ Joystick(JOYSTICK_DEFAULT_REPORT_ID, 
  JOYSTICK_TYPE_GAMEPAD, 0,
  JOYSTICK_DEFAULT_HATSWITCH_COUNT,
  false, false, false, false, false, false,
  false, false, false, false, false);

void setup() {

  // Initialize Joystick Library
  Joystick.begin();
}

int hatIndex=0;

void loop() {
    if (hatIndex == 0) {
        Joystick.setHatSwitch(0,-1);
        Joystick.setHatSwitch(1,0);
        hatIndex = 1;
    } else if (hatIndex == 1) {
        Joystick.setHatSwitch(0,0);
        Joystick.setHatSwitch(1,90);
        hatIndex = 2;
    } else if (hatIndex == 2) {
        Joystick.setHatSwitch(0,90);
        Joystick.setHatSwitch(1,180);
        hatIndex = 3;
    } else if (hatIndex == 3) {
        Joystick.setHatSwitch(0,180);
        Joystick.setHatSwitch(1,270);
        hatIndex = 4;
    } else if (hatIndex == 4) {
        Joystick.setHatSwitch(0,270);
        Joystick.setHatSwitch(1,-1);
        hatIndex = 0;
    }
    delay(500);
}

Additional context

I am not actually sure if this is an issue in this library or something with how the Linux kernel handles joystick/gamepad/other USB HID devices, but I am not enough of a programmer to figure it out.

Is it possible that linux is interpreting the USB descriptor in a more literal or strict way than older kernels and/or Windows are, and something in this library could be tweaked to work as expected?

I also tested on Kubuntu 21.04, Pop!_OS 21.04, Manjaro with identical results across kernels 5.4 and 5.12-xanmod.

MHeironimus / ArduinoJoystickLibrary