While upgrading my server, most probably while doing the upgrade to Ubuntu 20.04 Focal, mod-evasive got installed and enabled. It didn't effect the configured websites, except sometimes for a couple of seconds I received 403 errors. But finally everything continued working. The problem started, after adding a new website and trying to install a new Joomla platform. The installation process of Joomla stopped on the very last step without any error message on the screen.
By default OpenVPN runs on port 1194. This is quite nice, but often this port is not open in the firewalls. Therefor the OpenVPN server is unreachable. It also has advantages to run SSH on port 443. You may have fewer fake logins on the SSH server. In addition, port 22, or even any custom port such as 2020, is blocked by firewalls in most cases as well. If you simply put everything on port 443, this may not work, since Apache is already active for the SSL websites. And that's where SSLH jumps in.
If you have installed multiple PHP versions, you may want to be able to change the standard version without much effort. Log in to your server via SSH and enter the following command in the command line:
sudo update-alternatives --config php
If you reiceive the following error while starting phpmyadmin in your browser:
This page isn’t working Example.com is currently unable to handle this request. HTTP ERROR 500
Most probably you have a conflict with your PHP version after upgrading to Ubuntu 20.04. If you have different PHP Versions installed, you need to tell phpmyadmin which Version to use.
As soon as the basic installation of Joomla has been completed, the setup can be carried out. I had the following problem: the installer always stopped halfway without warning. Ultimately, it was because of the PHP version. Only after I changed the server configuration to PHP7.2 did the installation work properly. After the installation I was able to switch PHP back to 7.4. The problem was caused by the Apache mod-evasive module. For one thing, there were many 403 errors in the operation of Joomla and new installations could not be set up. For this reason, I first switched off this module: