Another approach would be:

• Use assuan_sock_accept which has consistent API with gnupg_fd_t

Fixed in: rP66abf7cb1e1b: Update GPL2 for new FSF address. Use URL for license.

works, tested with the provided example certs

information shows now up immediately, when the public key data is imported

On Windows with gpg4win 4.2.0 the filenames are suggested as in the description of this ticket, that is "Archive.tar (1).gpg".
But this is no issue, it can be decrypted with Kleopatra without any problem, anyway. The name of the decrypted folder is "Archiv.tar (1)" but it is a plain folder, no tar archive.

Fix pushed to the 23/07 branch and master.

On 64-bit Windows, the situation now is:

I am raising this up from the wishlist. Error messages from CRL errors can be so obscure, like we just had in a support call.

Use of FD2INT for the first argument of select is semantically not good. It's the number of file descriptor. When we use FD2INT here, the type is converted to 64-bit integer, then implicitly demoted to 32-bit integer. We need new macro, say, FD2NUM to convert FD into 32-bit integer.
<--- done in: rGea1935252e28: commond: Introduce FD2NUM to express conversion to number of fds.

Here is a test program for 64-bit Windows to see how cast works:

#include <stdint.h>
#include <stdio.h>

yeah, sorry, didn't test different key types yesterday.
NIST encryption keys do not work either, so only RSA encryption keys can be moved with Kleopatra to a smart card in gpg4win 4.2.0.
I can confirm that authentication keys work.

Found this one in Gpg4win-4.2.0-beta384:

There are some more surprising results like on my windows test keyring it would always report "5 new signatures" regardless of how often I ran the script ;)

Update the patch to allow --compatibility-flags hashing-in-parallel.

In T6379#172803, @ebo wrote:

Noticed in gpg4win 4.2.0-beta373:

For Brainpool and ed/cv25519 keys it is not possible to move a subkey to a smart card with Kleopatra. The error message is "invalid value".
Moving the main key works, though. The command line works for all keys types, of course.