Appium - File upload to web using Chrome - ERR_ACCESS_DENIED

I am trying to upload a file to https://the-internet.herokuapp.com/upload via Chrome using Appium. But it leads to ERR_ACCESS_DENIED error all the time.

The file resides in the Download folder of my device.

Refer the image below:

I have tried the following capabilities as well with different combinations, but it didn't help: noReset, autoGrantPermissions, fastReset.

My Script:

from appium import webdriver
import time

def execute_script():
  driver = webdriver.Remote(
      command_executor='http://0.0.0.0:4723/wd/hub',
      desired_capabilities={
          "platform": "android",
          "platformName": "android",
          "platformVersion": "10",
          "deviceName": "<xxxx>",
          "udid": "<xxxx>",
          "browserName": "chrome",
          "automationName": "UIAutomator2",
          "chromeOptions": {
              "w3c": False
          },
          # "autoGrantPermissions": True,
          # "noReset": True,
          # "fastReset": True,
          # "fullReset": False
      }
  )

  driver.get('https://the-internet.herokuapp.com/upload')

  up = driver.find_element_by_id("file-upload")
  up.send_keys("/sdcard/Download/file.pdf")
  driver.find_element_by_id("file-submit").click()

  driver.quit()

driver = execute_script()

The script executes fine till the send_keys step. But as soon as the file-submit click is performed, it leads to the mentioned error. I tried it on https://fileconvoy.com/ as well and it results in the same error.

Version Details:

• Appium Version: 1.17.0 (Tried version from 1.10.x to 1.20.x)
• Device: Samsung Galaxy S9, Android 10
• Chromedriver: 90.0.4430.24 (Tried for Chrome 81 as well, same error).

What all I have tried:

• Granted permissions via the following command explicitly before starting appium (and also midway of the script in case the permissions get reset), but no luck.

adb -P 5037 shell 'pm grant com.android.chrome android.permission.READ_EXTERNAL_STORAGE  android.permission.WRITE_EXTERNAL_STORAGE'

• Instead of using browserName: "Chrome", I have also tried specifying appPackage and appActivity to begin chrome. But no luck.

Is there anything that I am fundamentally missing? This works fine on desktop browsers (using selenium). But I haven't been able to run it once on my mobile device.

Let me know if there is anything else that I should share.

Have created an issue on Appium as well: https://github.com/appium/appium/issues/15293