I believe this particular error indicates that ECK is running with the webhook role enabled which should not be the case when you running in single namespace mode.
I think I have a theory about what is the problem in your case though: I am assuming you checked out the ECK code locally to run this make target and that code contains already changes incompatible with the 1.0.1 image you are trying to run. Most notably we have removed the concept of operator roles and the corresponding
--operator-roles parameter, which means the manifest you generated does not have the parameter and ECK defaults to all roles which includes the webhook role, causing your error.
- either checkout the code corresponding to the version of ECK you want to run (in your case 1.0.1) and re-generate the manifest again
- or you can manually edit the manifest you generated and add the missing roles flag. You want something like
args: ["manager", "--namespaces", "myns", "--operator-roles", "namespace,global"]