If you understand how to install CoreOS, you can also install OpenShift 4. You can provision CoreOS hosts using Foreman. In his talk at the Config Management Camp 2023, Jan explained how to do so, what obstacles there are, and how to use this solution to deploy an OpenShift cluster.
CoreOS is an immutable minimal version of Fedora Linux/Red Hat Enterprise Linux. There are automatic upgrades through rpm-ostree and zincati. It is popular thanks to its holistic approach and the fact that it allows container infrastructure to be immutable.
Once CoreOS has been set up, it is easy to install OpenShift. OpenShift is a Kubernetes distribution, offering a consistent experience for public-cloud, on-premise, hybrid-cloud, and edge architectures. You can use Foreman or orcharhino, our lifecycle management tool, to provision CoreOS hosts.