I tried it now on a fresh 7.4 and can confirm:
That’s right. Joomla has a static “powered by” link for instance, so mixed content is a Joomla “pb”.
Powered by <a href="http://www.joomla.org/">Joomla!®</a>
But there seems to be something strange with Joomla, HTTPS and rewriting.
On a running Joomla Site on my webhost following line in Joomla page source is rewritten to https:
but on NethServer it stays http:
What I did:
yum install http://mirror.de-labrusse.fr/NethServer/7/x86_64/nethserver-stephdl-1.0.6-1.ns7.sdl.noarch.rpm
yum install http://rpms.famillecollet.com/enterprise/remi-release-7.rpm
yum install nethserver-phpmyadmin nethserver-php-scl
chown -R apache:apache /var/lib/nethserver/vhost/joomla
If you force HTTPS on entire site in Joomla configuration which means set “public $force_ssl = ‘2’;” in configuration.php you get a redirect error.
No reverse proxying.
Chrome error message (sorry for German)
Found a howto, maybe we can improve it: