Towelroot is a great and simple root method,too bad is not working for new android version and on new devices. For S6 and s6 edge no longer need to worry if you were looking for something similar because is exact that, and is named pingpong root application. Exactly as towelroot ,can be done from your phone directly, without a computer, will not trip the knox flag or damage or warranty and is super simple and safe.
Supported S6 and S6 edge for pingpong root
Almost all versions of S6 and S6 edge are supported, and most firmwares,but if you want to be sure can verify here if your firmware is supported. Normally even if your firmware is not supported for rooting with pingpong root, but you still try it should just say phone not support and not damage the phone.
Step by step tutorial
A. Download from phone
1.Open your phone browser and search on google for "pingpong root", first result should be the official support forum from xda-developers.com,go there
2.Scroll down till the bottom ,and you should see the downloadable files attached ,download the last version available
3. Go to your downlaod folder using you File Manager application and will find the pingpongroot_beta6.apk
B.Transfer from pc
1.Downlaod the last pingpong root app from the xda oficial post
2. Connect the phone to the pc and transfer the file you just downlaoded to your phone
3.Using you File Manager go to the place from your phone where you transfer the pingpongroot app that you just transferred
B.Rest of the tutorial applies to both situations
4. Open the pingpongroot_beta6.apk,normally will give you an error saying "Install blocked ",but do not worry is normal just press "Setttings" button
5. You will be taken to Settings/Security and from there select to enable "Unknown sources"
6.This time the install should work again,the phone might asks if to continue the install sellect the option "Install anyway"
7. Once installation is complete,press Open and the program should install SuperSu,this is the program that basically manages the root acces
8.If you have not unselected last time the option "Allow this installation only" when enabling Unknown sources,now will ask you again to enable it,so please go and enable it again.
9.Once SuperSu is installed,do not open it as will give you an error, but instead go to your apps and open Pingpong root application
10.Press the button "Get root" and wait for the "Root done" message
11. If instead you receive a message that the phone is not yet supported press the button "Download data", and once that operation is done retry again by pressing "Get root"