Delete linkerd kubernetes namespace in "terminating" status
The error you experience is caused by the apiservice v1alpha1.tap.linkerd.io which is not working (ServiceNotFound). It is hard to say what have caused it but I can see two ways out of it:
If you don't need that API than simply delete it:
kubectl delete apiservice v1alpha1.tap.linkerd.io.If you need it, you can try to delete pods related to it in order to restart them and see if that helps.
After that you should be able to delete the namespace you mentioned.
Please let me know if that helps.
You can run linkerd uninstall | kubectl delete -f - and it will delete the resources in the right order so this error doesn't occur.