Debian Installation

Do not forget to change the default username/password.
Do not allow everybody to access the directory data from the URL.
Enable .htaccess if you use Apache (Option AllowOverride All).
This is your responsability to configure your server correctly.

Debian 10 (Buster)

Install Apache and PHP:

apt update
apt install -y apache2 libapache2-mod-php php-cli php-mbstring \
    php-sqlite3 php-opcache php-json php-ldap php-gd php-xml  \
    php-mysql php-pgsql php-curl php-zip

systemctl enable apache2

Install Kanboard:

version=1.2.13
wget https://github.com/kanboard/kanboard/archive/v$version.tar.gz
tar xzvf v$version.tar.gz -C /var/www/html/
chown -R www-data:www-data /var/www/html/kanboard-$version/data

rm v$version.tar.gz

Some features of Kanboard requires that you run a daily background job.