transactions – Need help moving funds from legacy address, Coldcard won’t sign psbt

It sounds like you imported only the xpub without the information that identifies where the xpub came from. This information, known as origin information, contains the fingerprint of the master key that derived your xpub, and the derivation path required to derive the xpub.

Coldcard refuses to sign saying “Failure. My XFP not involved”.

This indicates that the PSBT is missing the origin information needed for the Coldcard to determine whether a key was derived from the device’s master key. Since the Coldcard cannot store all keys that can be derived, it relies on the origin information being present and accurate. It checks to see whether the given master key fingerprints (which it calls XFP) match its own fingerprint, and if they do, it will try to derive the key with the derivation path contained in the PSBT.

The best possible solution is to import the xpub with the origin information. However I am not familiar with BlueWallet so I cannot provide instructions for how to do that.

You can also try using a different wallet software that does import with the origin information or provides facilities to setup an existing hardware wallet. I believe Sparrow and Electrum are able to do that.

Lastly, as you stated in a comment, you can import the seed itself. However as this puts the seed in use on a hot device, I would not recommend it as you then lose the benefits of using a hardware wallet.