How are you using git credential manager for 2fa on GitHub? They stopped supporting user/password auth for HTTPS git access a while back, and started requiring personal access tokens (which do not require a 2nd factor)
GCM will use an embedded browser so you can authenticate with the UI including your second factor, which will then give you a credential/token that can be used in the git environment over HTTPS. It's still a (differt, oath vs reference generation) token, but you aren't having to go generate, configure and update it yourself.