gpg-sq doesn't implement User ID matching the same as gpg-g10code
gpg(1) says you can ask for an exact match on a User ID by prefixing your search with an = sign:
HOW TO SPECIFY A USER ID
[…]
By exact match on OpenPGP user ID.
This is denoted by a leading equal sign. It does not make sense for X.509 certificates.
=Heinrich Heine <heinrichh@uni-duesseldorf.de>
This does not appear to work with gpg-sq:
0 dkg@alice:~$ gpg-sq --list-keys 'Justus Winter <justus@sequoia-pgp.org>'
pub rsa4064 2017-07-19 [C] [expires: 2024-07-18]
CBCD8F030588653EEDD7E2659B7DD433F254904A
uid [ full ] Justus Winter <justus@sequoia-pgp.org>
uid [ full ] <teythoon@uber.space>
uid [ full ] Justus Winter
uid [ unknown] Justus Winter <justus@gnupg.org>
uid [ unknown] Justus Winter <justus@pep.foundation>
uid [ unknown] Justus Winter <justuswinter@gmx.de>
sub rsa2048 2017-07-19 [A] [expires: 2024-07-18]
sub rsa2048 2017-07-19 [S] [expires: 2024-07-18]
sub rsa2048 2017-07-19 [E] [expires: 2024-07-18]
0 dkg@alice:~$ gpg-sq --list-keys '=Justus Winter <justus@sequoia-pgp.org>'
gpg: error reading key: No public key
2 dkg@alice:~$
This was first reported in https://bugs.debian.org/1070688