gist:5eec9d2adc3eaf1b755b0f666d745451

All digest-* packages built with the same GPG key:

$ gpg --list-keys
pub   rsa4096 2022-06-30 [SC]
      A5EA7083CF9513E99A476505B081E2685FE35E6E
uid           [ultimate] MNX Cloud Package Signing (Linux) <[email protected]>
sub   rsa4096 2022-06-30 [E]

digest-el7 built with:

$ gpg --version
gpg (GnuPG) 2.0.22
libgcrypt 1.5.3
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Home: ~/.gnupg
Supported algorithms:
Pubkey: RSA, ?, ?, ELG, DSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
        CAMELLIA128, CAMELLIA192, CAMELLIA256
Hash: MD5, SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2

digest-el8 built with:

$ gpg --version
gpg (GnuPG) 2.2.20
libgcrypt 1.8.5
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Home: /root/.gnupg
Supported algorithms:
Pubkey: RSA, ELG, DSA, ECDH, ECDSA, EDDSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
        CAMELLIA128, CAMELLIA192, CAMELLIA256
Hash: SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2

digest-el9 built with:

$ gpg --version
gpg (GnuPG) 2.3.3
libgcrypt 1.10.0-unknown
Copyright (C) 2021 Free Software Foundation, Inc.
License GNU GPL-3.0-or-later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Home: /root/.gnupg
Supported algorithms:
Pubkey: RSA, ELG, DSA, ECDH, ECDSA, EDDSA
Cipher: IDEA, 3DES, CAST5, BLOWFISH, AES, AES192, AES256, TWOFISH,
        CAMELLIA128, CAMELLIA192, CAMELLIA256
AEAD: EAX, OCB
Hash: SHA1, RIPEMD160, SHA256, SHA384, SHA512, SHA224
Compression: Uncompressed, ZIP, ZLIB, BZIP2

Reproduce on NetBSD:

$ ftp https://us-central.manta.mnx.io/pkgsrc/public/tmp/netpgp-vs-gpg/digest-el7-20220214.tgz
$ ftp https://us-central.manta.mnx.io/pkgsrc/public/tmp/netpgp-vs-gpg/digest-el8-20220214.tgz
$ ftp https://us-central.manta.mnx.io/pkgsrc/public/tmp/netpgp-vs-gpg/digest-el9-20220214.tgz
$ ftp https://us-central.manta.mnx.io/pkgsrc/public/tmp/netpgp-vs-gpg/linux.gpg

$ echo 'GPG_KEYRING_VERIFY=/root/linux.gpg' >/etc/pkg_install.conf

$ pkg_info -Q PKGPATH ./digest-el7-20220214.tgz 
pkgtools/digest
$ pkg_info -Q PKGPATH ./digest-el8-20220214.tgz  
pkg_info: unable to verify signature: Signature key id e99a476505b081e2 not found
$ pkg_info -Q PKGPATH ./digest-el9-20220214.tgz
pkg_info: unable to verify signature: Signature key id e99a476505b081e2 not found

With https://www.netbsd.org/~riastradh/tmp/20230603/netpgp_gpg2.patch applied pkg_info still fails but now with:

pkg_info: unable to verify signature: Signature key id 0000000000000000 not found

jperkin/gist:5eec9d2adc3eaf1b755b0f666d745451