How to convert ECDSA P256 curve signature to SECP256K1 curve? I would like to get the ATECC608A microchip to sign data with ECDSA secp256k1 curve, but the chip only signs using the P256 curve.

Is there an operation I can do using the original message and the signature under P256 that would produce a signature under secp256k1?
There is no way to convert a signature with one curve to another. If there were, one could trivially forge signatures by starting with an insecure curve and converting it to a signature in a secure curve.