Unverified signature using GitHub mirrored repository

I am using GitLab to mirror a GitHub repository for CI/CD. After merging a pull request using the GitHub UI, GitLab shows the commit as being unverified.

Github:
image
GitLab:
image

GitHub uses their own public GPG key to verify commits done using their UI. Is there any solution to this problem? I’m certain that this is a common situation that users of GitLab’s mirroring feature are running into.

More info on GitHub’s public GPG key: https://stackoverflow.com/questions/60482588/what-is-githubs-public-gpg-key

I’ve stumbled upon a closed issue of the same problem, which does not have a solution:

Thanks!