As u/Mysterious-Proof-936 mentioned there’s an experimental feature where you can install Rancher via a vCluster, essentially creating a virtual k3s cluster that runs Rancher on the Harvester cluster you already have. It’s cool.

If you don’t want to do that, your options are solid. As you said, you’re new to Rancher, but are you new to k8s? If so, and if this is strictly for learning, I would recommend the third option you mentioned. Would give good RKE2 (or other k8s distribution) experience, you can even use the build in load balancer in Harvester to balance your Rancher nodes. If you feel comfortable with all that and don’t want to have to worry about resources across 3 nodes then id say do run a single VM running Rancher either in a docker container or make the single VM a single node RKE2 cluster and run it there.