I found the solution !
Just add these lines

<VirtualHost *:80>
    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/html
    ServerName server_domain_name_or_IP
    <Directory /var/www/html/>
        AllowOverride All
    </Directory>
    . . .

on this file sudo nano /etc/apache2/sites-available/000-default.conf
& then sudo a2enmod rewrite & then sudo service apache2 restart

Thanks !

Thank you for sharing this. helped me resolve after hours of troubleshooting!

I have modified 000-default.conf and it looks like this:

<VirtualHost *:80>

    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/html
    ServerName 46.101.165.116

    <Directory /var/www/signature/>
       AllowOverride All
       </Directory>

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

</VirtualHost>

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet

and I ran the sudo commands but still I can't access /var/www/signature/ through the browser:
http://46.101.165.116/var/www/signature

Any idea what could go wrong?

It did not work for me. Please help

Open /etc/apache2/apache2.conf

Look for the line that says

<Directory /var/www/html>
    Options Indexes FollowSymLinks
    AllowOverride All
    Require all granted
</Directory>

and change it to

<Directory /var/www>
    Options Indexes FollowSymLinks
    AllowOverride All
    Require all granted
</Directory>

That should fix it.