A MAC is symmetric and can thus only be verified by you or somebody who you trust to not misuse or leak the key.

You sign them against a known public key, so anybody can verify them.

Regular digital signatures is what's needed here You can still use such a signing circuit but treat it as an attestation by the camera's owner, not as independent proof of authenticity.

If it's just the cameras owner attesting, then just have them sign it. No need for expensive complicated circuits and regulations forcing these into existence.