Unfortunately, only LDAP is currently supported. There is no implementation of Enterprise SSO like Oauth/SAML. It's planned for the future, but not in priority for now.

I have never tested Cinnamon, but it should work in theory, because it stores most of it's settings in dconf.

Custom scripts: deliberately not, so far. Once a management agent runs arbitrary scripts as root, it stops being a policy system and becomes remote-code-execution-as-a-service — the security review, the audit story, and the "what exactly is enforced on this machine?" It may be implemented in the future, but with a ENV variable/config property from the application configuration. The same goes for configuration management systems like Ansible.

Thank you for the interest! I'm interested in developing a community around the software.