Edit: Once you "grab" your input device with python-evdev (dev.grab()), the input will be absorbed until it is un-grabed (dev.ungrab()). If you grab your only keyboard input, you'll be stuck and will need a secondary keyboard to get unstuck.

I have a bad habit of speculating too much, I'm gonna try to stick to just what I did in case I'm remembering some of the why details incorrectly. I'll use the details from my device, anywhere you see "Azeron LTD Azeron Keypad", "16d0", or "1103", you need to replace the values with your device-

Start by finding the info for the input device you want to monitor:

cat /proc/bus/input/devices | more

This should result in a list of input devices with various details, I used the 'Name' to identify mine:

N: Name="Azeron LTD Azeron Keypad"

When you have found the device, save the vendor ID and product ID for the next step:

I: Bus=0003 Vendor=16d0 Product=1103 Version=0111
N: Name="Azeron LTD Azeron Keypad"

Add a udev rule so that you can read the input from the device, and another for python-evdev to create a virtual device. I use link_priority 71 (as seen in the file name). The rule I'm using to let the virtual device be created could be better - this is something you might want to research more for a permanent solution, but this rule can be removed later if you just wanted to test with it:

sudo nano /etc/udev/rules.d/71-azeron-uaccess.rules

Write the file contents:

#Access to read from "Azeron LTD Azeron Keypad"
SUBSYSTEMS=="usb", ATTRS{idVendor}=="16d0", ATTRS{idProduct}=="1103", TAG+="uaccess"

#Access for python-evdev to create a new device
KERNEL=="uinput", SUBSYSTEM=="misc", OPTIONS+="static_node=uinput", TAG+="uaccess", MODE="0660"

Restart udev:

sudo udevadm control --reload-rules && sudo udevadm trigger

At this point, you should have access to the device from python-evdev and also be able to create a virtual device with python-evdev. I don't know if it will help, but I figured I can add a bit of my code here:

import evdev, subprocess, re
from evdev import UInput, InputDevice, ecodes
from select import select

virtual_device_name = 'python-mouse-device'
input_mouse = '/dev/input/'
input_keyboard = '/dev/input/'

# These Regex's may need to be updated per-device. These match 
# my Azeron Cyro Mouse and Key Inputs.
input_keyboard_regex = "^.*Azeron_LTD_Azeron_Keypad_2053388B5942.*event-kbd.*"
input_mouse_regex = "^.*Azeron_LTD_Azeron_Keypad_2053388B5942.*event-mouse.*"

# Get the path to the input devices. These are dynamic, and can change on system reboot.
devices_by_id = subprocess.run(["ls", "-l", "/dev/input/by-id"], encoding='utf-8', stdout=subprocess.PIPE)
devices_by_id = devices_by_id.stdout.split('\n')

for device_id in devices_by_id:
    device_match = re.search(input_mouse_regex, device_id)
    if device_match:
        input_mouse = input_mouse + re.search("event[0-9]{1,}", device_match.group()).group()
        
    device_match = re.search(input_keyboard_regex, device_id)
    if device_match:
        input_keyboard = input_keyboard + re.search("event[0-9]{1,}", device_match.group()).group()

if input_mouse == '/dev/input/' or not input_mouse:
    sys.exit("Mouse not found")

if input_keyboard == '/dev/input/' or not input_keyboard:
    sys.exit("Keyboard not found")

#Create the virtual mouse
ui = UInput.from_device(InputDevice(input_mouse), name=virtual_device_name)

try:
	#Define the devices
	devices = map(InputDevice, (input_keyboard, input_mouse))
	devices = {dev.fd: dev for dev in devices}
	#for dev in devices.values(): print(dev)
	
	#Grab the devices to block their native input
	for dev in devices.values(): dev.grab()

	#Read and handle events from the devices and translate it to the virtual device
	r, w, x = select(devices, [], [])
	for fd in r:
		for event in devices[fd].read():
			if event.type == ecodes.EV_MSC and event.code == 4 and event.value == 458767:
				#remap or add a script to perform
			#Add more if / elif as needed for different keys or key combinations

			#If you didn't remap the key, pass the input through as normal
			ui.write(event.type, event.code, event.value)
finally:
	for dev in devices.values(): dev.ungrab()

The code above I run as a service, but my explanation is getting a bit long-winded already, so if any of this ends up being helpful, and you actually do want to run it as a background service, if you need help doing that let me know!