Cannot export SSH public key

[Felix E. Klee]

So `gpg --card-status` imports [SC] and [E], but not [A]:

    $ rm ~/.gnupg/private-keys-v1.d/*
    $ ls -a1 ~/.gnupg/private-keys-v1.d/
    .
    ..
    $ gpg --card-status
    […]
    Signature key ....: 7A0F E73D DB74 4F0F 9734  1DA7 1BE3 49D1 1B6E
    D589
          created ....: 2023-06-29 03:50:43
    Encryption key....: DBBD 3239 D0F1 4326 808D  FC8F 7CC0 2D68 D2E3
    1736
          created ....: 2023-06-29 03:50:43
    Authentication key: 7A0F E73D DB74 4F0F 9734  1DA7 1BE3 49D1 1B6E
    D589
          created ....: 2023-06-29 03:50:43
    […]
    sec>  rsa4096/1BE349D11B6ED589  created: 2023-06-29  expires: never
                                    card-no: 0006 18698016
    ssb>  rsa4096/7CC02D68D2E31736  created: 2023-06-29  expires: never
                                    card-no: 0006 18698016
    ssb#  rsa4096/32B106F6877CC64B  created: 2023-11-22  expires: never
    $ gpg --list-keys --keyid-format LONG --with-keygrip yubikey at f76.eu
    pub   rsa4096/1BE349D11B6ED589 2023-06-29 [SC]
          7A0FE73DDB744F0F97341DA71BE349D11B6ED589
          Keygrip = 0E67508AC6866D82ABB95E0B53CF5D18DC48A786
    uid                 [ultimate] Felix E. Klee (YubiKey) <yubikey@[…]>
    sub   rsa4096/7CC02D68D2E31736 2023-06-29 [E]
          Keygrip = 07D6164F019D2EDF59C650992CF93776B2DD17F2
    sub   rsa4096/32B106F6877CC64B 2023-11-22 [A]
          Keygrip = 9C67E5BBB72EF0BF2625792F8F134CE4FD961FF5
    $ ls -a1 ~/.gnupg/private-keys-v1.d/
    .
    ..
    07D6164F019D2EDF59C650992CF93776B2DD17F2.key
    0E67508AC6866D82ABB95E0B53CF5D18DC48A786.key

To me it looks like [A] is on the Yubikey, as it should.

*But how do I get the private key stub for [A] imported?*