How to completely disable (again) image signing and verification ?

[nipil]

I am using Debians's 12 podman 4.3.1 version.

I configured podman to sign and verify using GPG keys (through policy.json)

I podman image sign a couple image, and verified that

• i can pull the signed ones
• i cannot pull the non-signed ones

Then i tried to "unconfigure" image signing (deleted policy.json, default.yaml and removed sigstore folders).

Now when i podman push harbor.example.org/test-project/test-sig:latest i get the following message :

Error: Copying this image would require changing layer representation, which we cannot do: "Would invalidate signatures"

If i add the --remove-signatures options, i can push the image into the registry with success.

But if i later push again without adding the --remove-signatures option, i get the same message.

My questions are :

1. AFAIK GPG signatures are not stored in the remote registry (this is no OCI artefact, like Notation does), so as i purged the sigstore folder and deconfigured, how/where does podman find/detect a signature ?
2. If the --remove signature does what it says it does, as i deconfigured GPG signing, and used it once, i should not require it for later push, as there should not be any signature left
3. As i am using Harbor 2.12, is there anything to do on the registry side when deconfiguring GPG image signing ?

Thanks in advance for any feedback