Signing Helm packages using DCT

I’m trying sign all the images that are in our Azure container registry using Docker Content Trust. I was able to sign all the docker images but getting the following error when trying to pull and sign the Helm package.
Does docker support signing helm packages? Any document or article that I can go through for singing helm packages. I appreciate your help in resolving this issue. Thanks!!!

4.1.4: Pulling from ingress-nginx

unsupported media type application/vnd.cncf.helm.config.v1+json

Error response from daemon: No such image: <acr_registry_name>