I created an Apache web server on Ubuntu 18.04.2 LTS, using the guide described here. Afterwards the web server worked completely fine.
Later on I installed Libvirt onto the web server, after which the web server stopped working. So i uninstalled it along with the "virbr0" network bridge it created.
The web server still did not work afterwards so I used
sudo netstat -nap and found that apache2 was unable to bind/access port 80 on IPv4 but it was able to on IPv6.
How do I allow apache2 to have access to port 80 on IPv4?