I recently upgraded Firefox to the latest build.

Then, my geckodriver binary stopped working in Python.

firefox --version
Mozilla Firefox 71.0

python --version
Python 3.8.0

/bin/geckodriver --version
geckodriver 0.24.0

The main problem, I had an outdated Geckodriver version (from the distro repo)

sudo pacman -R geckodriver
/bin/geckodriver --version
bash: /bin/geckodriver: No such file or directory

Find the latest version

https://github.com/mozilla/geckodriver/releases/

cd /opt
sudo wget https://github.com/mozilla/geckodriver/releases/download/v0.26.0/geckodriver-v0.26.0-linux64.tar.gz

sudo tar -xzvf geckodriver.tar.gz && rm -f geckodriver.tar.gz

sudo chmod +x geckodriver

sudo chmod 755 geckodriver

sudo cp geckodriver /bin/geckodriver

Geckordriver should be updated to the latest version:

geckodriver --version
geckodriver 0.26.0