This is a first stable release of the DebOps stable-3.1 branch. Due to a long development phase, there are lots of new features (new roles, improved support for the systemd ecosystem, new features of the DebOps scripts and more). Users can find details in the official Changelog, which is available on the documentation website.
You can check the changes from the previous release as well as the changes since v3.1.0 release using the GitHub interface. The changelog for the stable-3.1 branch in the HTML format is available on the DebOps documentation website.