Selenium can't find file from '/tmp/' directory to populate file-input

I want to upload a file using the selenium Firefox driver. The file is dynamically generated and does not need to persist so I would like to place it under /tmp/.

While selecting files from my home directory works perfectly fine:

from selenium import webdriver
from pathlib import Path

driver = webdriver.Firefox()
driver.get("https://viljamis.com/filetest/")
Path(f"{Path.home()}/my_test_file").touch()
driver.find_element('xpath', '//input[@type="file"]').send_keys(f"{Path.home()}/my_test_file")

doing the same with a file located at /tmp/my_test_file like so:

from selenium import webdriver
from pathlib import Path

driver = webdriver.Firefox()
driver.get("https://viljamis.com/filetest/")
Path(f"/tmp/my_test_file").touch()
driver.find_element('xpath', '//input[@type="file"]').send_keys(f"/tmp/my_test_file")

results in the following crude error message:

Traceback (most recent call last):
  File "/home/username/Downloads/test.py", line 12, in <module>
    driver.find_element('xpath', '//input[@type="file"]').send_keys(f"/tmp/my_test_file")
  File "/home/username/.local/lib/python3.10/site-packages/selenium/webdriver/remote/webelement.py", line 233, in send_keys
    self._execute(
  File "/home/username/.local/lib/python3.10/site-packages/selenium/webdriver/remote/webelement.py", line 410, in _execute
    return self._parent.execute(command, params)
  File "/home/username/.local/lib/python3.10/site-packages/selenium/webdriver/remote/webdriver.py", line 444, in execute
    self.error_handler.check_response(response)
  File "/home/username/.local/lib/python3.10/site-packages/selenium/webdriver/remote/errorhandler.py", line 249, in check_response
    raise exception_class(message, screen, stacktrace)
selenium.common.exceptions.InvalidArgumentException: Message: File not found: /tmp/my_test_file
Stacktrace:
RemoteError@chrome://remote/content/shared/RemoteError.sys.mjs:8:8
WebDriverError@chrome://remote/content/shared/webdriver/Errors.sys.mjs:182:5
InvalidArgumentError@chrome://remote/content/shared/webdriver/Errors.sys.mjs:311:5
interaction.uploadFiles@chrome://remote/content/marionette/interaction.sys.mjs:537:13

which is strange because the file definitly does exist

I can't find a way to make it work. Why is there a difference when selecting files from /tmp/?

The access-rights are both times -rw-rw-r-- and manually selecting the file by clicking the "browse..." button and selecting the file also works perfectly fine.

Edit: I am running a fairly fresh installation of Kubuntu 22.04.1

Faced the same problem on Ubuntu 22.04, installing firefox as .deb (Not a Snap) helped me.

1. Remove the Firefox Snap:

sudo snap remove firefox

2. Add the (Ubuntu) Mozilla team PPA to your list of software sources:

sudo add-apt-repository ppa:mozillateam/ppa

3. Change Firefox package priority:

echo ' Package: * Pin: release o=LP-PPA-mozillateam Pin-Priority: 1001 ' | sudo tee /etc/apt/preferences.d/mozilla-firefox

4. Setup firefox auto-updates:

echo 'Unattended-Upgrade::Allowed-Origins:: "LP-PPA-mozillateam:${distro_codename}";' | sudo tee /etc/apt/apt.conf.d/51unattended-upgrades-firefox

5. Install Firefox via apt

sudo apt install firefox

Used the following instruction: https://www.omgubuntu.co.uk/2022/04/how-to-install-firefox-deb-apt-ubuntu-22-04