“If you use Thunderbird’s or GnuPG’s function for generating keys directly on-card, it will propose you a backup. But this is a backup of the encryption subkey only!” - from the FAQ.
This backup creats a sk_.gpg file. How do I import this?
gpg --import sk_<id>.gpg gives “gpg: key : no user ID”. Tried with both a fresh .gnupg folder and one that has the cards public keys.