Good question (and yeah we need to put more out there), so the FROST multisig only has a single group public key (one xpub). And this single group public key can be reconstructed from secret shares or their images. That means that so long as you have two devices or their backups, you can find the xpub and simple derivation path -> descriptor.

@nick thanks for your answer! Coming back here after your appearance at CD175. How can one device verify the receive address? I thought you need the threshold for that. Does this mean the xpub is stored on each device but encrypted through the app? Or can anyone finding one device see all transactions?