I have tried running OKD/OpenShift locally - even using the latest retake on it - Code Ready Containers. It is way too resource intensive for a single VM. That is before you start the prometheus/monitoring/alerting stuff or metrics server - at that point your single VM is good as dead.

You can just learn plain old K8S - get an Ubuntu VM and snap install microk8s. Add another vm as a node and it works well for most part and sans storage stuff (you can do NFS though) you can learn almost everything. After that catching up to OpenShift specifics is not that big of a deal - it's not all that different.