The Libgcrypt version you are using has not been build from git or a released tarballs. Only with a released tarball you would get no suffix. With git bou will see a -betaNNNN suffix.

Because a user in https://mstdn.social/deck/@GnuPG/113011825339406300 did read the documentation, I had a look in the documentation and in other public definitions (e.g. https://www.gnu.org/software/tar/manual/html_node/Formats.html#Formats) and I can understand the questions of the user.

gpgtar is compatible to PGP Desktop's format which they call ZIP. This is technically ustar with the most common extensions. Don't let us go into yet another TAR format discussion.

Good idea. Done for master and gnupg24

Right, thanks for the information. Might I suggest printing a warning when --keyring is given?

The --keyring option is deprecated and does not work at all if the keyboxd is used. This is the default for a new GnuPG 2.4 installation.