I do not know why this information is not more readily available. It is a very important piese of information, needed for any modifications brought into .htaccess file.
Posted by @Oblivion here: The "Strict-Transport-Security" HTTP header is not set to at least "15552000" seconds. For enhanced security, it is recommended to enable HSTS - #26 by justyoshi, he mentions:
.htaccess needs to be enabled with AllowOverride
This is the first thing that should be verified. If the AllowOverride directive is set to None then this will disable all .htaccess files. In order to verify this, you must open the Apache configuration file (typically either called httpd.conf or apache.conf) and check that the AllowOverride directive is set to AllowOverride All. If you needed to make changes to your Apache config, remember to save the file and restart Apache. sudo service apache2 restart
Which means /etc/apache2/apache2.conf NEEDS to have AllowOverride All under <Directory /var/www/>.
Good piese of information and advice, thanks to Oblivion. This really needs to be in the tutorial for installing Nextcloud. At least as a verification on things not working with .htaccess configs.