The best open source alternative to Ansible is Puppet, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to Ansible and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Ansible are Salt (Free, Open Source), Chef (Free, Open Source), pyinfra (Free, Open Source) and Terraform (Free, Open Source).
Fleet Commander is an application that allows you to manage the desktop configuration of a large network of users and workstations/laptops. It is primarily targeted to Linux systems based on the GNOME desktop.