@chrishamm I believe I found it in the manual Raspian installation instructions.
.... If you wish to use the latest unstable DSF components, you can run the following commands instead:wget -q https://pkg.duet3d.com/duet3d.gpg wget -q https://pkg.duet3d.com/duet3d-unstable.list sudo mv duet3d.gpg /etc/apt/trusted.gpg.d/ sudo mv duet3d-unstable.list /etc/apt/sources.list.d/duet3d-unstable.list sudo chown root:root /etc/apt/trusted.gpg.d/duet3d.gpg sudo chown root:root /etc/apt/sources.list.d/duet3d-unstable.list
Please be aware that the unstable repository is meant for beta testers and that it can contain experimental code. For production use, the stable repository is strongly recommended.
In case you were using the stock package feed, make sure to remove it before you run apt-get:sudo rm /etc/apt/sources.list.d/duet3d.list