RHACS supports verifying image signatures with Sigstore format today. This feature is to extend signature verification support in ACS for Container images signed using GPG Keys  

RedHat signing and verifying images stored in container registeries in both format today, see https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/building_running_and_managing_containers/assembly_signing-container-images_building-running-and-managing-containers#proc_signing-container-images-with-gpg-signatures_assembly_signing-container-images

and  https://docs.openshift.com/container-platform/4.18/security/container_security/security-container-signature.html#containers-signature-verify-enable_security-container-signature