Generating an self-installing anaconda-iso from any bootc container that has simple signature (as opposed to cosign/sigstore) will fail to build.

Workaround:

Remove the input signatures from the container image, using e.g.

$ skopeo copy --no-signatures docker://registry.redhat.io/rhel9-beta/rhel-bootc:9.4 docker://quay.io/examplecorp/myrhel

Then create an anaconda-iso for quay.io/examplecorp/myrhel.