A Tanzu Kubernetes release provides the Kubernetes software distribution signed and supported by VMware for Tanzu Kubernetes Grid 2.0 clusters on the Supervisor. Before you upgrade the Supervisor to a later version, you must verify that the Tanzu Kubernetes Grid clusters are of Kubernetes version that is compatible with version of Supervisor to which you want to upgrade.

Tanzu Kubernetes releases Release Notes

For a list of all Tanzu Kubernetes releases, see the release notes.

Kubernetes Release Versions Supported with vSphere 8 of Tanzu Kubernetes Grid

Before upgrading the vSphere with Tanzu infrastructure, including vCenter Server and Supervisors to vSphere 8, make sure that all your Tanzu Kubernetes Grid cluster are of version 1.21 or 1.23 preferably. If a Tanzu Kubernetes Grid cluster is incompatible with vSphere 8, upgrade the cluster before proceeding with the system upgrade.

Use Kubectl to List Available Tanzu Kubernetes releases

You can list Tanzu Kubernetes releases and view the compatibility and updatability for each release using following command. 
kubectl get tanzukubernetesreleases
The COMPATIBLE column indicates if that Tanzu Kubernetes release is compatible with the current Supervisor. The UPDATES AVAILABLE column indicates if there is a Kubernetes upgrade available and the recommended next Tanzu Kubernetes releases to be used. 
NAME                                VERSION                          READY   COMPATIBLE   CREATED   UPDATES AVAILABLE
v1.18.15---vmware.1-tkg.1.600e412   1.18.15+vmware.1-tkg.1.600e412   True    True         21h       [1.19.7+vmware.1-tkg.1.fc82c41]
v1.19.7---vmware.1-tkg.1.fc82c41    1.19.7+vmware.1-tkg.1.fc82c41    True    True         21h       [1.20.2+vmware.1-tkg.1.1d4f79a]
v1.20.2---vmware.1-tkg.1.1d4f79a    1.20.2+vmware.1-tkg.1.1d4f79a    True    True         21h

This same information is also available using kubectl get tkc <tkgs-cluster-name>.