Android rooting from Ubuntu
Have you tried KingRoot? It looks like the only non-Odin method, but I haven't tried it. 

Install KingRoot (enable external sources to install)

Run KingRoot

Tap "Try to Root"

Check success with Root Checker app (available on Google Play)

link to download:
http://forum.xda-developers.com/devdb/project/dl/?id=13663

My source:
http://trueandroid.com/how-to-root-samsung-galaxy-tab-s-8-4-sm-t705-without-pc/
Here's some extra info on it: http://forum.xda-developers.com/android/apps-games/one-click-root-tool-android-2-x-5-0-t3107461