How to automatically deploy routers / industrial PC's
Regarding no requirements on the target device, of the tools you mention, only Ansible does not need an agent on the host. The minimal requirement to use Ansible modules is Python on the host you want to update. If you don't have Python on hosts you could even send raw commands to the hosts.

Wikipedia has a list comparing configuration management software, there you can find other agent-less tools.

Not listed on Wikipedia is Fabric, a simple Python library to execute remote shell commands. It is agent-less as well.