Installing language-pack-tr-base fixed the issue. Closing. Sorry for the noise.

In T7454#196228, @werner wrote:

Actually not a bug: In my tests I forgot to unset LANGUAGES and LANG before calling gpg.

LANGUAGE= LANG= LC_MESSAGES=de_DE gpg

Thus this should work. But it did only work when I used

LANGUAGE= LANG= LC_MESSAGES=de_DE.UTF8 gpg

Thus the whole thing is related to the configuration of locale.alias and on whether LANGUAGE is set in the environment (for me it is set to en_US:en

In T7454#196094, @werner wrote:

Does

gpg --version

show English or Turkish strings?

In T7454#195889, @ikloecker wrote:

Which dialogs? pinentry? If yes, then your assumption is correct. pinentry also gets the texts from GnuPG.

This is the formula: https://github.com/Homebrew/homebrew-core/blob/c26f1c8714c231ee6796915f033ba229c89af3d6/Formula/gnupg.rb

This is the Homebrew build. Maybe something not included in the recipe?

gpgconf -L:

sysconfdir:/usr/local/etc/gnupg
bindir:/usr/local/Cellar/gnupg/2.4.0/bin
libexecdir:/usr/local/Cellar/gnupg/2.4.0/libexec
libdir:/usr/local/Cellar/gnupg/2.4.0/lib/gnupg
datadir:/usr/local/Cellar/gnupg/2.4.0/share/gnupg
localedir:/usr/local/Cellar/gnupg/2.4.0/share/locale
socketdir:/Users/emirsari/.gnupg
dirmngr-socket:/Users/emirsari/.gnupg/S.dirmngr
keyboxd-socket:/Users/emirsari/.gnupg/S.keyboxd
agent-ssh-socket:/Users/emirsari/.gnupg/S.gpg-agent.ssh
agent-extra-socket:/Users/emirsari/.gnupg/S.gpg-agent.extra
agent-browser-socket:/Users/emirsari/.gnupg/S.gpg-agent.browser
agent-socket:/Users/emirsari/.gnupg/S.gpg-agent
homedir:/Users/emirsari/.gnupg