This DOI refers to ET_2019_10 releases of the two codes that comprise the Einstein Toolkit:
The Cactus code, which is checked out using "einsteintoolkit.th"
The SelfForce-1D Code (which is checked out using
git clone --single-branch --branch ET_2019_10 https://bitbucket.org/peterdiener/selfforce-1d.git)
See https://einsteintoolkit.org/download.html for more detailed instructions on downloading and installing the software.