I have a couple general questions about https://github.com/rancherfederal/rke2-ansible & figured this might be a good place to ask. - Can rke2-ansible be used to upgrade RKE2, in addition to just installing RKE2? - What is the purpose of the “Testing Play” (testing.yml). Is it intended to test the health of the cluster, post install; or is it more to just test the Ansible code itself?

The testing play is for testing ansible code in CI integration testing. As for upgrade, I don't believe you can upgrade without downtime based on this GH issue. https://github.com/rancherfederal/rke2-ansible/issues/295 If you are using Rancher, using the system-upgrade-controller is more robust.