It seems with some updates in Debian 10, your installation script is now broken. It is producing numerous errors, and missing requirements it needs. For example, "dig" and "curl" is missing at the beginning. Maybe you should have the script include those.

Other errors include problems with UFW and fail2ban spitting out errors when trying to install.
There are a few more errors, but the script goes past them quite fast.

In addition, I have noticed on older installs of Debian 10 which were successful, after an update, the web UI will is no longer able to connect to the database and will show "Class 'CI_Controller' not found"

Maybe you can take a look and fix the script.

CentOS 7 seems unaffected