Installing my favorite web suite aka Hubzilla on Debian is a joy. Quick, straightforward and easy. I will show you how to do it in about 10 minutes or less.
Edit 09.09.2019:
Updated, tested with Debian 9 "Buster" and for ]PHP-FPM / Apache Event Worker. There are more tuning tips in Mark Nowiasz' tuning tips for Hubzilla, highly recommended for further reference. You will not be finished with this basic quickstart howto. Read the Wiki, there are valuable information to help you adapt your server config to your needs.

Installing my favorite web suite aka Hubzilla on Debian is a joy. Quick, straightforward and easy. I will show you how to do it in about 10 minutes or less.
Edit 09.09.2019:
Updated, tested with Debian 9 "Buster" and for ]PHP-FPM / Apache Event Worker. There are more tuning tips in Mark Nowiasz' tuning tips for Hubzilla, highly recommended for further reference. You will not be finished with this basic quickstart howto. Read the Wiki, there are valuable information to help you adapt your server config to your needs.

What you will need:

• Debian basic installation (only deviation in my install was including "basic" and SSH-server, which actually makes sense as you need a way to remote control your system, and fail2ban t give you a little protection for brute force login attempts. Chose your passwords wisely but never enter them into foreign services. Though this may be useful to get some impession on password security.)
• Existing domain, correctly configured and pointing to your server
  

All right then, let's start the Hubzilla installation party.

• The Basics: Install the required dependencies:
  apt install openssh-server git apache2 mariadb-server php-fpm php-curl php-gd php-mbstring php-xml php-mysql php-zip imagemagick certbot python-certbot-apache php-fpm fail2ban
  
• Webserver Apache: Create vhost file /etc/apache2/sites-available/hubzilla.conf and enable vhost, enable the required apache module rewrite. You need to replace example.com with your own domain name.
  MyDomain=example.com
  Then paste this into your shell.
  

  
  cat > /etc/apache2/sites-available/hubzilla.conf << EOF
  <VirtualHost *:80> 
      ServerAdmin webmaster@localhost
      ServerName $MyDomain
      DocumentRoot /var/www/hubzilla
      ProxyPassMatch ^/(.*\.php(/.*)?)$ unix:/run/php/php7.3-fpm.sock|fcgi://localhost/var/www/hubzilla
      <Directory />
          Options FollowSymLinks
          AllowOverride All
      </Directory>
      <Directory /var/www/>
          Options Indexes FollowSymLinks 
          AllowOverride All
          Order allow,deny
          allow from all
      </Directory>
      ErrorLog ${APACHE_LOG_DIR}/hubzilla_error.log
      LogLevel warn
      CustomLog ${APACHE_LOG_DIR}/hubzilla_access.log combined
  </VirtualHost>
  EOF

  
  Enable the new vhost
  a2ensite hubzilla
  You might want to disable the default site (enabled automatically upon installation):
  a2dissite 000-default.conf
  Enable apache modules rewrite
  a2enmod rewrite
  Enable apache modules mpm_event and proxy
  a2enmod mpm_event
  Restart apache2 in order to activate all these changes
  systemctl restart apache2
• Download Hubzilla: clone the Hubzilla Git repository and chown everything to be writable to the webserver account www-data
  cd /var/www/ ; git clone https://framagit.org/hubzilla/core.git hubzilla; chown -R www-data. hubzilla;
• To create the database set your desired password first:
  MyPassword=SuperSecret
  Then actually create the database:
  

  mysql -u root -e "create database hubzilla ; CREATE USER 'hubzilla'@'localhost' IDENTIFIED BY '$MyPassword'; GRANT ALL PRIVILEGES ON hubzilla.* to 'hubzilla'@'localhost';"
  

• SSL Encryption: create the letscencrypt certificates in order to use SSL and have certbot automatically configure your apache vhost to use SSL. Just follow the instructions. Let certbot configure your vhost to use SSL.
  certbot
• setup a cronjob
  echo "*/10 * * * *    www-data cd /var/www/hubzilla; /usr/bin/php Zotlabs/Daemon/Master.php Cron > /dev/null 2>&1"  >> /etc/crontab
• Install the official addons:
  util/add_addon_repo https://framagit.org/hubzilla/addons addons-official
  

Continue with:
Howto: Hubzilla Server Setup On A Working Web Server for the actual Hubzilla setup

This short howto will document the Hubzilla installation dialogues. It assumes you already have got a running web server and cli access. You will need a LAMP or similar and a domain set up properly including a working certificate, for example issued by letsencrypt.

Install Hubzilla on an existing web server

This short howto will document the Hubzilla installation dialogues. It assumes you already have got a running web server and cli access. You will need a LAMP or similar and a domain set up properly including a working certificate, for example issued by letsencrypt.
For a more detailed documentation, please refer to the installation readme install/INSTALL.txt.

• Create database

  You need to manually create the database. For that you can use any tool you like, be it PHPMyAdmin or similar. Or just good old CLI.
  Please substitute <myhub> for your own data, and especially the password <myhubpw> must be changed.
  create database myhub ; CREATE USER 'myhub'@'localhost' IDENTIFIED BY 'myhub'; GRANT ALL PRIVILEGES ON test.* to 'myhub'@'localhost' IDENTIFIED BY 'myhubpw'; GRANT ALL PRIVILEGES ON myhub.* to 'myhub'@'localhost';
  Note: Postgres is also supported if you prefer that one, though the initial development happened for MySQL / MariaDB.

• Git clone the repository

  Git cloning the software onto your server is the recommended way to put the Hubzilla software on your server, as this is required for the recommended way to update and maintain your hub.
  Just go into your web root and issue
  git clone https://framagit.org/hubzilla/core.git myhub

• Browser based installatiaon

  Now you are ready to call your Hubzilla domain from the browser. It will also launch into the installation process.
  
  

  Hubzilla Server Setup: System Check

  You will be greeted by a system check that will tell you if there are any packages left you will need to install. As is to be expected, you will not be able to proceed before you resolve all possible issues.
  Please note: The upload file size information is just that, an information. You will be able to proceed no matter how small or huge that value is.
  
  
  

  Hubzilla Server Setup: Database Connection

  As mentioned, you can also opt for using Postgres. This is to be selected below.
  
  
  

  Hubzilla Server Setup - Site Settings

  The basic site settings include just three values:
  
  • Your designated admin account email-address:
    You are surely going to create an account once you finish your installation. It is recommended to set up the first account using exactly this address as using this address will make the corresponding account an admin account.
  • The website URL:
    The URL should be https://... if it is not, please stop and install a certificate, for example let's encrypt. The easiest way is just to install certbot and then to call certbot and follow the on-screen help. It's pretty good. Or ask your admin / your service provider.
  • Your time zone:
    To select your time zone you can also start typing the one you are looking for, for example the city "Berlin" if you are living in Germany and therefore want your hub to run on a German time zone.
    
  ,
  
  

  Hubzilla Server Setup: Installation Succeeded

  Now you should get the final success message which includes  a link to the registration page and the information that you will need to set up a cronjob for Hubzilla. Read on.
  
  

  Create your admin account and channel

  As mentioned above, follow the given link to the registration page. This article explains the process of account registration and channel creation in more detail. Please go there for more information.
  
  

  Cronjob

  As you can see in the screenshot above, you are being referred to the file install/INSTALL.txt for further information. You can read the extended information in section 8. This is just a short version: Add something like the below line to your /etc/crontab, though you will certainly adapt this to your own needs, this is only a hint and cannot be used literally.
  
  • Certainly you can chose other values than every ten minutes.
  • You will supposedly substitute www-data with your web server's system account for any non-Debian based systems.
  • Check that your php executable is really at /usr/bin/php, if not please change appropriately.
  • Check your document root and change the example /var/www/myhub to your path.
  • The rest should remain as is, Zotlabs/Daemon/Master.php Cron > /dev/null 2>&1
    
  
  */10 * * * *    www-data cd /var/www/myhub; /usr/bin/php Zotlabs/Daemon/Master.php Cron > /dev/null 2>&1