.htaccess is disabled by default in Ubuntu 16. ModRewrite could also be disabled. Here are the two steps needed to activate pretty permalink and all the other stuff related to .htaccess.
sudo a2enmod rewrite sudo service apache2 restart
Edit the Apache main configuration file to activate .htaccess
Open the main configuration file for Apache:
sudo nano /etc/apache2/apache2.conf
Search for the expression “Options Indexes FollowSymLinks“. Do this by pressing “CTRL + W” and paste the phrase into the Nano search field.
Find the following three lines:
Options Indexes FollowSymLinks AllowOverride None Require all granted
Change the word “None” to “All”.
The correct version would look like this:
Options Indexes FollowSymLinks AllowOverride All Require all granted
Then restart Apache again
sudo service apache2 restart