Unfortunately the Beta build of Marshmallow for the Galaxy S6 and S6 Edge is only available for the UK variant. If you are willing to tinker around a bit you can actually run the Marshmallow Beta build on other variants. If you are able to get 6.0 loaded on your S6 or S6 Edge you can actually root it!
To root you will need to download SuperSU 2.64 on your phone. You will also need ODIN on your PC. Put your phone into download mode, in Odin uncheck auto reboot, Install oldsboot.tar, reboot into download mode (volume down+power button+home button), install custom recovery, boot into recovery, install supersu in recovery mode, after installation is finished reboot your device, when the recovery ask do not select "yes-root", in odin install the newsboot.tar. During the first boot-up your device will reboot once. Enjoy your rooted marshmallow device.
via XDA