To the best of my knowledge, docker login will log you into dokcerhub. In that case, dockerhub does not support GPG authentication, only password and token.

Mybe what you're looking for is using token which can be achieved like below:

How to Generate a Personal Access Token in Dockerhub:

1. Log in to your Docker Hub account: Docker Hub.
2. Go to Account Settings > Security.
3. Click New Access Token. Use this token in place of your password during docker login.

In case this is not what you're looking for, could you please provide more info. Do you get the stated error immediately you type docker login or do you get the error after you input some values after docker login?