skopeo copy adds manifest-list signature removal and sparse-list stripping
When copying only selected platforms from a multi-architecture image to a registry that rejects sparse lists, use `--strip-removed-platforms` and explicitly remove signatures. Use `--remove-list-signatures` to preserve per-instance signatures, or `--remove-signatures` to remove all signatures.
skopeo copy --multi-arch=linux/amd64,linux/arm64 --strip-removed-platforms --remove-list-signatures docker://quay.io/skopeo/stable:latest docker://registry.example.com/skopeo:latest