I had some issues while trying to get GPG signing working while using GitHub Desktop. While their docs say the application doesn’t support GPG, a bunch of users seemed to have it working.
I ran into a few errors and got it working correctly. A “gpg failed to sign the data” error is what took a while to find a fix for.
Assuming you followed all the instructions in GitHub’s docs, also make sure your global git settings are pointing to the gpg command and signing is set to true:
user.signingkey=EEDDA4EE375C6D12 gpg.program=/usr/local/bin/gpg commit.gpgsign=true
And what ultimately fixed my issue was disabling GPG terminal output via:
echo "no-tty" >> ~/.gnupg/gpg.conf