Deployment OCP 4.15.10 with IBI seem to complete fine.
Using the kubeconfig file generated for the spoke/IBI results in the following error:

error: tls: found a certificate rather than a key in the PEM for the private key

If I ssh into the spoke and use /etc/kubernetes/static-pod-resources/kube-apiserver-certs/secrets/node-kubeconfigs/lb-ext.kubeconfig - it works fine and shows that the cluster is deployed.