You need to configure GitHub to use Azure Active Directory (Azure AD) for authentication.

When you connect to a Git repository from your Git client for the first time, the credential manager prompts for credentials. Provide your Microsoft account or Azure AD credentials.

Note: Git Credential Managers simplify authentication with your Azure Repos Git repositories. Credential managers let you use the same credentials that you use for the Azure DevOps Services web portal. Credential managers support multi-factor authentication through Microsoft account or Azure Active Directory (Azure AD). Besides supporting multi-factor authentication with Azure Repos, credential managers also support two-factor authentication with GitHub repositories.