gnupg – Can’t get `gpg –auto-key-retrieve –verify` to work

I am trying to automate the compilation of the newest GCC on my dev machine, and I’d like to automatically verify the signature of the tarball too. However, I can’t get gpg --auto-key-retrieve to work:

gcc# gpg --auto-key-retrieve --verify gcc-11.1.0.tar.xz.sig tarballs/gcc-11.1.0.tar.xz
gpg: Signature made Tue Apr 27 12:39:44 2021 CEST
gpg:                using RSA key 6C35B99309B5FA62
gpg: Can't check signature: No public key

If I manually retrieve the key, it works just fine (and the gpg --verify succeeds as well):

gcc# gpg --recv-keys 6C35B99309B5FA62
gpg: /home/user/.gnupg/trustdb.gpg: trustdb created
gpg: key 6C35B99309B5FA62: public key "..." imported
gpg: Total number processed: 1
gpg:               imported: 1

(default keyserver used in the above is https://keys.openpgp.org:443)

I’ve tried:

  • --keyserver-options auto-key-retrieve,
  • manually specifying the server,
  • auto-key-locate (though I’ve learned this has nothing to do with my use case).

What am I doing wrong?

I’m running gpg version 2.2.19 on Ubuntu 20.04.2 and working on files originally from http://ftp.gnu.org/gnu/gcc/gcc-11.1.0/.