Hi @rhessinger,
I currently do not have an overview on how many images without top-level mediaType.
To have an image in Nexus without top-level mediaType, you can use the oras CLI tool to manipulate the manifest.
For my testing, I used skopeo to copy an OCI image (e.g. alpine/git:v2.52.0) to Nexus.
skopeo copy --dest-creds <user>:<password> --dest-tls-verify=false docker://alpine/git:v2.52.0 docker://registry.nexus.example/docker/alpine/git:v2.52.0
Then I used the oras to:
-
fetch the manifest
oras manifest fetch --insecure registry.nexus.example/docker/alpine/git:v2.52.0 > manifest.json
-
Edit the manifest.json, and remove the top-level mediaType
-
Push the manifest back to the registry
oras manifest push --insecure --media-type application/vnd.oci.image.manifest.v1+json registry.nexus.example/docker/alpine/git:v2.52.0 manifest.json
After that, when inspecting the manifest with docker manifest inspect, the top-level mediaType should be missing from the image. And when trying to do migration in ProGet, it will show that the image is not found.
I hope the information shared above is useful. Thank you.