QGIS 2.12 & Ubuntu 14.04 SAGA installation not found

Installing QGIS 2.12 on Ubuntu 14.04 from the debian trusty ppa. Upon opening QGIS I notice the following error under the Processing tab:

Problem with SAGA installation: SAGA was not found 
or is not correctly installed

If I execute sudo apt-get install saga I then get that the version installed (2.1) is unsupported.

I did make sure to "properly" purge QGIS before installing as in QGIS install on Ubuntu 14.04 fails

Looking inside ~/.qgis2/python/plugins/processing/algs folder it does seem like SAGA is installed... but how to get QGIS to recognize it?

Answer

Per @wildintellect's suggestion:

1. 
   

   I changed package sources from qgis.org/debian to ubuntugis, so my /etc/apt/sources.list looks like

   
   

   deb http://qgis.org/ubuntugis trusty main
   deb-src http://qgis.org/ubuntugis trusty main
   deb     http://ppa.launchpad.net/ubuntugis/ubuntugis-unstable/ubuntu trusty main
   




2. 
   

   Next I purged qgis using sudo apt-get --purge remove qgis python-qgis qgis-plugin-grass

   
   


3. Purge extraneous packages with sudo apt-get autoremove


4. Update repositories with sudo apt-get update


5. Install sudo apt-get install qgis python-qgis qgis-plugin-grass saga (note saga in that command).

After this, no more warning of a missing install.